Pocket Watch Parts & their Description

Pocket Watch Parts

Ever wonder what that term or description of a watch or clock part means? Well, wonder no more. Here is the most comprehensive list of watch and clock parts, meanings and descriptions that you will find anywhere on the Web.

Feel free to use any of these elsewhere on the web, but only with proper attribution:

ADJUSTED
ADJUSTABLE POTENCE
AFFIX
ALL-OR-NOTHING PIECE
AMPLITUDE
ANTI-MAGNETIC
APPLIQUE
ARBOR
ARC
ATTACHMENT
AUTOMATIC WATCH
AUTOMATON WATCH
AUXILIARY COMPENSATION
BACK PLATE
BALANCE COCK
BALANCE SPRING
BALANCE STAFF
BALANCE
BANKING PIN
BAR
BARREL HANGING
BARREL RESTING
BARREL (GOING)
Beat
BARROWS REGULATOR
BASSE TATILLE ENAMEL
BASSINE
BEETLE HAND
BEZEL
BIMETALLIC
BOTTOM PLATE
BOW
BRIDGE
BREGUET BALANCE SPRING
BREGUET HANDS
BREGUET KEY
BREGUET OVERCOIL
BREGUET STOP WORK
BRISTLE
BULLS EYE GLASS
BUSH
BUTTON WINDING
CADRATURE
CALIBRE
CAM
CANISTER CASE
CANNON PINION
CAP JEWEL
CAPPED MOVEMENT
CARTOUCHE DIAL
CENTRE PINION
CENTRE SECONDS
CENTRE WHEEL
CHAFF CUTTER
CHAISE WATCH
CHAMPLEVE
CHAPTER RING
CHASING
CHATELAINE
CHINESE DUPLEX
CHRONOGRAPH
CHRONOMETER
CHRONOSCOPE
CLICK
CLOCK WATCH
CLOCKMAKERS COMPANY
CLOISONNE
CLUB FOOT VERGE
CLUB TOOTHED LEVER
COCK
COLLET
COLOURED GOLD
COMPENSATED BALANCE
COMPENSATION CURB
COMPLICATED WORK
CONICAL PIVOT
CONSTANT FORCE ESCAPEMENT
CONSULAR CASE
CONTRATE WHEEL
CONVERSION
COQUERET
COUNT WHEEL
COUNTERPOISE PALLETS
CRANK LEVER ESCAPEMENT
CRANK ROLLER
CRESCENT
CROWN WHEEL ESCAPEMENT
CURB COMPENSATION
CURB PINS
CUT BIMETALLIC BALANCE
CUVETTE
CYLINDER ESCAPEMENT
CYLINDER PLUGS
DART
DEAD BEAT ESCAPEMENT
DEAD BEAT VERGE
DEAT PIECE
DEBAUFRE ESCAPEMENT
DECK WATCH
DEPTH
DETACHED ESCAPEMENT
DETENT ESCAPEMENT
DETENT
DIFFERENTIAL DIAL
DIVIDED LIFT
DOME
DOUBLE ROLLER
DOUBLE-BOTTOM CASE
DRAW
DROP
DUMB-REPEATER
DUPLEX-ESCAPEMENT
DUST-CAP
DUTCH FORGERIES
EBAUCHE
END SHAKE
END STONE
ENDLESS SCREW
ENGINE TURNING
ENGLISH LEVER ESCAPEMENT
ENTRY PALLET
EQUATION OF TIME
ESCAPEMENT
ESCAPE WHEEL
EXIT PALLET
FALSE PENDULUM
FIGURE PLATE
FIVE-MINUTE REPEATER
FLAGS
FLIRT
FLOATING HOUR DIAL
FLY
FLY-BACK HAND
FOB CHAIN
FOLIOT
FORGERIES
FORK
FOURTH WHEEL
FORM WATCH
FOUR-COLOURED GOLD
FRAME
FREE-SPRUNG
FRICTIONAL REST ESCAPEMENT
FULL PLATE
FUSEE
FUSEE CHAIN
GADROONING
GATE
GATHERING PALLET
GIMBALS SUSPENSION
GOING BARREL
GOING FUSEE
GOING TRAIN
GONGS
GRANDE SONNERIE
GREAT WHEEL
GUARD PIN
GUILLOCHE
HAIRSPRING
HALF PLATE
HALF-QUARTER
HALLMARK
HAND-SETTING
HANGING BARREL
HEART PIECE
HELICAL SPRING
HOG’S BRISTLE
HOOKE’S LAW
HORIZONTAL ESCAPEMENT
HORNS
HOUR RACK
HOUR WHEEL
HUNTER
IMPULSE
IMPULSE ANGLE
IMPULSE PALLET
IMPULSE PIN
INDEPENDENT SECONDS
INDEX
ISOCHRONOUS
JACQUEMART
JEWELS
JUMP-HOUR
JUMPING-HOURS
JUMPING-SECONDS
KARRUSEL
KEYLESS WATCH
KEYLESS WINDING
LEPINE CALIBRE
LEVER ESCAPEMENT
LEVER NOTCH
LIFT
LIGNE
LOCK(ING)
LOCKING PLATE
LUNETTE
MAINSPRING
MAINTAINING POWER
MALTESE CROSS
MARINE CHRONOMETER
MASSEY LEVER ESCAPEMENT
MEAN TIME
MIDDLE TEMPERATURE ERROR
MINUTE REPEATER
MOCK PENDULUM
MOON HAND
MOTION WORK
MOVEMENT
MUSICAL WATCH
NIELLO
NOTCH
NUREMBERG EGG
OIL SINK
OIGNON
OPENFACE
ORMSKIRK
OUTER CASE
OVERCOIL
PAIR-CASE
PALLET
PARACHUTE
PASSING CRESCENT
PASSING SPRING
PEDOMETER WATCH
PEDOMETER-WIND
PENDANT
PENDULUM WATCH (DIAL)
PERPETUAL CALENDAR
PERPETUAL WATCH
PILLARS
PILLARPLATE
PINION
PINCHBECK
PIN WORK
PIQUE
PIROUETTE
PIVOT
PIVOTED DETENT
PLATES
POISE
POKER HAND
POSITIONAL ERROR
POTENCE
POTENCE PLATE
POUZAIT ESCAPEMENT
PUMP-WIND
PULSE-PIECE
PURITAN WATCH
QUARTER RACK
QUARTER REPEATER
RACK
RACK LEVER ESCAPEMENT
RACK STRIKING
RATCHET WHEEL
RATE
RECOIL
RECOIL ESCAPEMENT
REGULATION
REGULATOR
REMONTOIRE
REMONTOIRE ESCAPEMENT
REPEATER
REPOUSSE
REPUBLICAN CALENDAR
RESILIENT ESCAPEMENT
ROBIN ESCAPEMENT
ROLLER
ROSKOPF
RUBY CYLINDER ESCAPEMENT
RUN-TO-BANKING
S BALANCE
SAFETY ROLLER
SAFETY DART
SAVAGE TWO-PIN
SAVONNETTE
SECONDS PINION
SECRET SIGNATURE
SECRET SPRING
SELF-COMPENSATING SPRING
SELF-WINDING
SET-UP
SHIP’S CHRONOMETER
SINGLE ROLLER
SIX-HOUR DIAL
SKELETON DIAL
SKELETONISED MOVEMENT
SNAIL
SOUSCRIPTION (MONTRE A)
SPLIT-SECONDS
SPRING BARREL
SPRING DETENT
STACKFREED
STANDING BARREL
STOP-WORK
STRAIGHT LINE LEVER
STRIP COMPENSATION
STUD
SUGAR TONGS
SUN AND MOON DIAL
SUPPLEMENTARY ARC
SURPRISE PIECE
SWEEP SECONDS
SWING WHEEL
SWISS LEVER ESCAPEMENT
TABLE ROLLER
TACT
TAILLE DOUCE
TAMBOUR CASE
TANGENT SCREW
TEMPERATURE COMPENSATION
TERMINAL CURVES
THIRD WHEEL
THREE-QUARTER PLATE
TIMING IN POSITIONS
TIMING SCREWS
TINTED GOLD
TIPSY-KEY
TOMPION REGULATOR
TOP PLATE
TOUCH PINS
TOURBILLON
TRAIN
TRIAL NUMBER
TRIPLE-CASED
TRIPPING
TURKISH MARKET WATCHES
TWO-PIN ESCAPEMENT
UNDER-DIAL WORK
UP-AND-DOWN DIAL
VERGE
VERGE ESCAPEMENT
VIRGULE ESCAPEMENT
WANDERING HOUR DIAL
WARNING
WATCH PAPER
WINDING SQUARE
WORM WHEEL

ADJUSTED. - The term "adjusted" simply means that the watch has been calibrated and keeps time under various conditions. These conditions could be temperature, meaning that for any temperature the watch will maintain accurate time. Also it could mean that the watch keeps accurate time in various positions, i.e, face up, face down, stem facing left, stem facing right. Most watches are also calibrated to maintain a constant time as the main spring is winding down.

'ALL-OR-NOTHING' PIECE. - This is used in better quality repeating watches and ensures that the hour striking mechanism is only struck when a push-piece is pushed fully home. (Ref: Richard French, "Servicing a Quarter Repeater" http://www.bhi.co.uk/hj/HJ-0404-133-138.pdf).

AMPLITUDE. - The frequency that the pendulum or balance makes.

ANTI-MAGNETIC. - A metal object that has either been demagnetised or a metal that does not exhibit a natural tendency to be affected by magnetic fields.

ARBOR. - In watch terms an arbor is an axle used for any gear wheel or winding wheel.

ATTACHMENT. - The lugs of a watch case that attach to a watch band (United States Patent 4847820

AUTOMATON WATCH. - Watches that at certain time points, for example when striking hours, have animated figures that move in time with the chime of the watch.

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AUTOMATIC OR SELF-WINDING WATCH. - A watch where the mainspring is wound by the action of the movement of the watch when the wearer moves during normal daily activities.

AUXILIARY COMPENSATION. - John Sweetman Eiffe first proposed to correct "middle temperature error" by way of an auxiliary compensation device. (Ref: The Marine Chronometer by Rupert Gould pages 181 - 183). Middle temperature error refers to a watch tending to operate faster when it is corrected for errors at extreme temperatures.

BALANCE WHEEL. - The wheel in a watch that swings back and forward in a regular beat, allowing the watch to maintain a constant time. In a watch the balance wheel is the equivalent to a clocks pendulum.

BALANCE SPRING. - The balance spring controls the regularity of the balance wheel, expanding and contracting to allow the regular spinning motion of the balance wheel to be controlled. Balance springs are protected from the problems associated with changes in temperature by the use of bi-metallic strips.

BALANCE STAFF. - The balance staff is the center spindle or axle of the balance wheel.

BANKING PIN. - Any pin in a movement that limits the movement of a lever to prevent damage.

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BARREL (GOING). - The barrel contains the mainspring which when wound gives its energy out to the drive train, controlled by a toothed section on the exterior.

BEAT. - A description of the ticking sound made by the movement.

BEZEL. - The exterior part on the face of a watch surrounding the face and holding the crystal in place.

BIMETALLIC. - Commonly known as a Bi-Metalic strip, invented by John Harrison, it composes of two different materials sandwiched together, each strip having a different co-efficiency of expansion which has the effect of countering any expansion or contraction due to changes in temperature.

BOW. - Usually in Pocket Watches, the bow is used to attach a chain to the watch. Usually over the crown.

BRIDGE. - An additional part fixed to the main plate, forming the frame of the watch.

BULL'S EYE GLASS. - A glass lens with a round flat smooth surface machined in the center.

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ADJUSTABLE POTENCE. - The potence is a bracket that supports a pivot. An adjustable potence allows the escapement action to be adjusted without having to dismantle the movement. Some can be adjusted with a screwdriver, while others require a key for adjustment.

AFFIX. - A bimetallic blade that is connected to the balance rim to alter and affect the compensating arrangement.

APPLIQUE. - Term used for ornaments or attached to the casing or numerals or decorations attached to the watch dial.

ARC. - The balance of a watch has an arc that is twice the size of the amplitude. For example, if a balance has an amplitude of 250 degrees, the arc would be 500 degrees.

BACK PLATE. - Also known as the top plate. The back plate in a clock is the one located furthest from the dial. Some call it the potence plate.

BALANCE COCK. - Also known as the cock, this is a bracket that connects the movement plate to the pivot of a wheel. It has evolved from a simple s-shaped support to an elaborately decorated part of the mechanism. Watches made in different countries may sport different shapes in their balance cocks. The way the balance cock is formed can be very useful in dating a watch.

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BALANCE SCREWS. - Also known as timing screws, these screws are adjusted to set the time.

BAR. - Similar to a cock, but a bar has a foot which secures it to the movement plate. Also known as a bridge.

BARREL (HANGING). - Also called a standing barrel, this is a going barrel attached to the movement by its upper portion beneath a cock or bridge.

BARREL (RESTING). - Mounted in an arbor, the great wheel receives power through a ratchet and click system where the spring is enclosed inside a barrel screwed to the plate.

BARROW’S REGULATOR. - Found in balance spring watches; this is a very early form of regulator made of two curb pins that are held upright in a slide. The pins embrace the end of a straight balance spring, and the slide moves along a keyed endless screw. The movement plate is engraved with an index to show how much the slide can be moved with the key. It is rare to find a watch with an intact Barrow’s regulator.

BASSE-TAILLE ENAMEL. - Translucent enamel over an engraving; serves to enhance the artistic effect.

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BASSINE. - A model of watch case with rounded, smooth edges.

BEETLE HAND. - A model of hour hand that slightly resembles a stag beetle. Usually paired with a poker hand for the minutes.

BOTTOM PLATE. - A metal plate that holds the movement parts and bridges.

BREGUET BALANCE SPRING. - An improvement made to balance springs by using a flat spiral spring with an overcoil, developed by Abraham Louis Breguet, a Swiss horologist who worked in Paris, France.

BREGUET HANDS. - Blue pomme hands used on watches by Abraham Louis Breguet. The hands have a hollowed tip. This design is now referred to as Breguet hands.

BREGUET KEY. - Invented in 1789 by Abraham Louis Breguet, this ratchet key prevented winding the watch in the wrong direction. It worked by using a compressed spring. The upper portion of the key turned the lower portion when moved in the right direction, but the lower portion would slip if turned in the wrong direction, saving the watch from damage. Also known as a tipsy key.

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BREGUET OVERCOIL. - Also known as the Breguet balance spring. What made it different from other balance springs was the highest exterior turn of the spring was raised, preventing the spring from moving out of its rotational axis.

BREGUET STOP-WORK. - A stop-work with two toothed wheels. One wheel has eight teeth and is fixed to the barrel arbor. The other wheel has ten teeth and is fixed directly to the barrel. The two wheels have projections which meet after four turns, limiting the the amount of winding the mainspring can do.

BRISTLE. - A thick flexible hair or bristle commonly found in early German watches. Short bristles would be used as banking pins. Long bristles were used occasionally, with one end fixed. The bristle would be flexed by two pins on the rim of the balance. Shorter bristles caused a faster rate of movement. Bristles provided more elasticity in the balance action.

BUSH. - Also known as bouchon. The bush is a hard brass tube used to make pivot holes in watch plates.

BUTTON, WINDING. - The knob affixed to the top of a stem or shaft used to wind a watch or set the hands. Usually round, with a milled or knurled texture to make a secure grip. Also called a set-hand button.

CADRATURE. - Also known as motion work. This mechanism lies just behind the dial near the front plate. It transmits the rotation of the movement to the watch hands. Sometimes this term also applies to the calendar, alarm work or striking if they are outside the plates.

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CALIBRE. - Coined by Sully around 1715, this term denotes the layout and dimensions of a movement.

CAM. - An irregularly shaped cylinder or disc that is contacted by a lever designed to follow the contour of the disc.

CANISTER CASE. - An early type of watch case, shaped like a drum. Slightly similar to a tambour case, without a hinge.

CANNON PINION. - The part of the motion work that carries the minute hand on a watch. It is a hollow pipe or arbor, fit on the center wheel arbor by friction to allow the hand to be set.

CAP JEWEL. - A cone shaped pivot made from a low grade or synthetic jewel. Always paired with hole jewels to give less friction and better performance.

CAPPED MOVEMENT. - A movement covered with a cap to protect it from dust.

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CARTOUCHE DIAL. - Popular on French and other continental watches. A cartouche dial is made of white enameled plaques adorned with black or blue numerals. The plaques are fired to a metal dial. May include the maker’s name.

CENTRE PINION. - Centrally located in the movement, this pinion is driven by the great wheel.

CENTRE SECONDS. - Also known as sweep seconds, this is a second hand that pivots in the middle of the dial with the minute and hour hands, which may be on a secondary dial.

CENTRE WHEEL. - A central wheel which supports the arbor that carries the minute hand.

CHAFF-CUTTER. - An escapement derived from the Debaufre escapement, developed in 1704 by Peter Debaufre. It gets its name from the shape of the teeth on the escape wheel.

CHAISE-WATCH. - A large travelling watch, not to be confused with a carriage clock.

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CHAMPLEVE. - A piece of metal that has been hollowed by a graver to allow enamelling to adhere to it. A Champleve dial is a metal dial that has had portions removed; it was common on some watches to hollow out the numerals and minute markings so they could be filled with pitch, colored wax or enamel.

CHAPTER RING. - Also known as an hour ring, this is the ring that is engraved with the hours and minute gradations are engraved. Some watches don’t have the minutes marked, only the half and quarter hours.

CHASING. - Engraving on the front of a piece of metal that creates a relief effect by creating grooves, furrows, indentations and channels.

CHATELAINE. - A chain designed to hold a lady’s watch or jewelry. In the case of a watch, it was common to also attach the winding key and other trinkets for adornment. The chain was often designed to go along with the decoration on the watch case.

CHINESE DUPLEX. - Invented by C. E. Jacot in 1830, this was a duplex escapement most frequently used in watches exported to China. There is a double set of locking teeth to control the movement. After the first tooth of each set passed the roller, the escape wheel locked in position, so a second swing of the balance was needed to unlock the second tooth and let the second hand move forward. The intermediate stage is seen by a slight movement of the second hand between beats.

CHRONOGRAPH. - A watch that has a second hand that can be started, stopped and zeroed using a slide or push-piece. An additional dial is there to record the number of revolutions or minutes counted by the second hand.

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CHRONOMETER. - Basically, any instrument used to measure time. This term has also been used by different groups to describe specific timepieces. The English watchmakers, for instance, consider a chronometer to be a portable clock or watch with a detent escapement, although they used the term before detent escapements were developed. In the Swiss and French watchmaking circles, a chronometer is a watch that has been given an official rating certificate by the observatories at Neuchatel or Geneva.

CHRONOSCOPE. - A device capable of measuring small units of time. Some use the term to also describe an instrument used to test watches during repair work.

CLICK. - A lever or pawl with a beak-like shape to engage the ratchet-shaped teeth on a wheel. This lever can be pivoted, and is under tension by a spring. Clicks allow a wheel to turn in one direction only. Most watches allow the mainspring to be wound; this tension is held against the click.

CLOCKMAKERS’ COMPANY. - Granted a Royal Charter in 1631, the Worshipful Company of Clockmakers regulated the order, manner and form in which clocks were made in England. Apprentices joined Guilds, and once they had finished their training, could work on their own as clockmakers. The Clockmakers’ Company held sway in a ten mile radius of London. It could search and inspect all watches and clocks made in England and those imported from abroad. Those deemed unworthy could be destroyed or ordered to be repaired to their specifications. Before its inception, clock and watchmaking trades were controlled by the Blacksmiths’ Company.

CLOCK-WATCH. - A watch designed to strike the hours; these types of watches have been made since the beginnings of watchmaking. Not the same as a repeating watch.

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CLOISONNE. - French for compartments. Designs are made using wire (usually gold) to form small areas. The areas are filled with colored enamel, then fired. Once polished, the design is highly decorative.

CLUB-FOOT VERGE. - A derivative of the escapement made by Debaufre in 1704, using a frictional-rest dead-beat movement. Also called the dead-beat verge or Ormskirk escapement, after the English town in Lancashire where this escapement was popular in the early 1800s.

CLUB-TOOTHED LEVER. - Usually found in continental lever watches, this lever escapement used a club-toothed escape wheel instead of a pointed-toothed escape wheel. This wheel uses a lift divided between the pallet stones and the impulse faces on the teeth. Pointed-toothed wheels get the lift entirely by pallet stones.

COCK. - A bracket with one end attached to the movement plate and the other supporting the pivot of a wheel. Balance cocks are mounted on the top plate of the movement and support the top pivot of the balance staff. In early watches, the balance cock was a simple S shape. Eventually, the cock was decorated more elaborately, especially on the foot and table. The foot is the portion of the cock attached to the plate. The table provides the bearing for the top pivot on the balance staff. English balance cocks, like those just described, can also be found occasionally in Swiss, Dutch and German watches from the early 1700s. French and continental cocks are usually round or oval. They have lateral lugs to hold the fixing screws, making it more of a bridge than a cock. The highest quality watch cocks date between 1625 and the early 1700s. Balance cocks are often used to date a watch.

COLLET. - A collar or washer used to secure something, like the hand collet, which is used to secure the fitting of the watch hands.

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COLOURED GOLD. - Gold is colored with various alloys to produce yellow, silver, green or red hues. Coloured gold is used to decorate watch cases, dials and jewelry. Also known as tinted gold.

COMPENSATED BALANCE. - A balance inside a watch used to compensate for the effects heat and cold may have on the mechanism. In 1859, Airy showed that a chronometer lost 11 seconds in 24 hours for every degree in Fahrenheit that the temperature rose. Pierre Le Roy attempted to compensate for this loss using a balance. A bimetallic balance was eventually created by Thomas Earnshaw. Modern watches use a metal alloy balance with an alloyed balance spring to prevent loss of time due to temperature.

COMPENSATION CURB. - First used by John Harrison, the compensation curb is a bar made of brass and steel. It is fixed at one end. The other end moves freely and features curb pins. Rising and falling temperatures cause the strip to bend in shape, moving the curb pins along the balance spring. The common form of this curb is U shaped. It has one curb pin attached to the free end. As the curb bends, the pin either moves away from the spring in cold temperatures, or closer to the spring in hot temperatures. This allows the watch to compensate for changes in temperature and keep time more accurately. Breguet used the U shaped compensation curb; it was used frequently in France in the early 1800s.

COMPLICATED WORK. - A mechanism on a clock or watch engaged in something other than timekeeping. Examples include repeating, chronograph work, calendar work, and so on. Complicated works became a specialization in La Valee de Joux, Switzerland, during the latter half of the 1800s.

CONICAL PIVOT. - This pivot is narrower at the top than at the base. The friction for this type of pivot occurs only at the tip of the pinion. This type of pivot is used most frequently on the balance wheel, and occasionally on the escape wheel.

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CONSULAR CASE. - Named for Napolean, who was Consul of France at the time this was introduced. This is a watch case with a double bottom that has been fitted with a high, rounded glass. When the bottom is opened on its hinge, a second back is shown, featuring two holes for hand setting and winding. The watch movement swings out from the front of the case when the bezel is opened.

CONSTANT FORCE ESCAPEMENT. - This is an escapement where the impulse is powered by a spring kept tensioned by the going train. It is termed constant because the impulse delivery is not affected by irregularities caused by power fluctuations. Related to remontoire.

CONTRATE WHEEL. - A wheel whose teeth are positioned at right angles to the wheel’s plane. In a verge escapement, this wheel drives the escape wheel pinion.

CONVERSION. - When one type of escapement is replaced with another. For example, a lever escapement could be converted with a verge escapement.

COQUERET. - The steel end plate that holds the balance staff pivot in place. Used from around 1735 until jewelling became common.

COUNT WHEEL. - This wheel controls the number of hours struck. It is located in the striking train and consists of a series of 11 notches. The notches are located on the wheel’s periphery at increasing distances apart. A lever or detent slides over the raised sections and drops into each slot as the wheel turns. Whenever the detent is lifted, the striking train runs, allowing the watch to strike as many times as possible before the detent falls into the next slot. No projection is necessary for half hours or one o’clock, as the detent is lifted for enough time to allow a single strike. This simple system works fairly well, though it chimes in a regular progression, without any reference to the hour hand’s position. Also known as the locking plate. This system has been replaced by rack-striking.

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COUNTERPOISE-PALLETS. - This part was added to some high quality Swiss levers in the 1800s to balance the watch. The counterpoise, pallet arms and fork were filed out of a single piece.

CRANK LEVER ESCAPEMENT. - Designed by Edward Massey in 1814, the crank lever escapement was derived from the Lither-land rack lever. A roller took the place of the pinion and the rack was removed. The roller was attached to the staff. It had an impulse pin that looked like a single leaf of a pinion that projected from the roller’s circumference. A square notch was cut in the lever’s end for the impulse pin. Two prongs extended from either side of the notch, providing a safety to prevent the lever from getting out of engagement. Not long after, the surface of the impulse pin became a jewel; not long after, the entire pin was replaced with a jewel. Also known as Massey’s escapement. The original form did not contain a draw, though later versions did. The crank lever led to the single table roller.

CRANK ROLLER. - Also known as a crank lever escapement. See above description.

CROWN-WHEEL ESCAPEMENT. - Also known as the verge escapement. The escape wheel is shaped somewhat like a medieval crown, hence the name.

CRESCENT. - The hollow cut in the roller of a lever escapement that lets the dart or guard pin pass. The cut is shaped like a crescent.

CURB COMPENSATION. - The compensation curb is a bar made of brass and steel that is fixed at one end. The other end moves freely and features curb pins. Changing temperatures cause the strip to bend in shape, moving the curb pins along the balance spring. The most common form of this curb is shaped like a U with a single curb pin attached to the free end. As the curb bends, the pin moves away from the spring in cold temperatures, or closer to the spring as the temperature rises. This compensates for changes in temperature and keeps time more accurately.

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CURB-PINS. - Also known as index pins. These two pins enclose the balance spring at its outer end, close to its attachment. The pins are attached to the index, or regulator. The pins adjust the time of vibration of a balance by altering their position. Moving them outward increases the length of the spring and the watch may lose time; if moved inward, the length of the spring is decreased. Increasing the distance between the curb-pins also acts to lengthen the spring.

CUT BIMETALLIC BALANCE. - A balance made of two metals, such as brass and steel.

CUVETTE. - The inside cover that protects the movement. It is hinged and sprung. Usually made of brass, even in good quality gold watches from the continent. The cuvette often has holes in it for winding and setting the time by hand. It may be engraved with the name of the watchmaker, movement number, number of jewels in the movement and the type of escapement in the watch.

CYLINDER ESCAPEMENT. - Also known as a horizontal escapement. Introduced in 1726 by George Graham, the cylinder escapement features fifteen horizontal teeth on the escape wheel. A cylinder is mounted on the balance staff, part of which is cut away to allow the teeth to enter as the balance swings and rotates the wheel. As each tooth enters the cylinder, it makes an impulse toward the balance, resting inside the cylinder until the supplementary arc, or oscillation, is complete and it returns to its original place, freeing the tooth. The next tooth enters and repeats the process.

CYLINDER PLUGS. - Plugs for the top and bottom of the cylinder that form pivots for the balance staff.

DART. - Also known as a guard-pin. The dart is a safety device in a lever escapement, located on the lever nearest the balance. It prevents the escape wheel from unlocking except by an impulse pin. Sometimes called a safety pin.

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DEAD-BEAT ESCAPEMENT. - The escape wheel does not recoil in this type of escapement. A cylinder escapement is an example of a dead-beat escapement.

DEAD-BEAT VERGE. - Derived from the Debaufre escapement. Two pallets with bevelled edges are found on the balance staff. Each pallet receive an impulse in each direction from the teeth of the escape wheel in succession.

DEBAUFRE ESCAPEMENT. - Developed by Peter Debaufre in 1704, this escapement is a frictional rest, dead-beat escapement. It has two escape wheels that rotate on the same axis. Their teeth are saw cut, each moving alternately with the other in a staggered pattern. The balance staff passes between them. A pallet is affixed to the balance staff. A tooth from the escape wheels rests on the flat surface of the pallet while the balance is moving until the tooth slides down the slope of the pallet. The teeth of the wheel alternate resting on the pallet, then give impulse to the balance without a recoil. Chaff-cutter escapements and club-foot verges are derived from the Debaufre escapement. A similar escapement was designed by Henry Sully; another was made in Ormskirk in Lancashire, England.

DEAF-PIECE. - Also known as a pulse-piece or sourdine. This pin projects through a hole in the bottom of the case from the edge of a repeating movement. A piece known as the finger is held against the pin to receive the strikes from the hammer to chime the hours.

DECK WATCH. - A large, accurate watch used on ships to calculate the ship’s position.

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DEPTH. - The amount of meshing, or the degree of penetration, between gears. If the meshing is too much, the depth is described as being too great. If not enough, the depth is too shallow. If the gears are not set properly, accurate timekeeping is difficult.

DETACHED ESCAPEMENT. - Also known as a lever escapement. They were specifically called detached escapements or detached levers to make the difference between them and rack levers clear. This is an escapement that has the controller free or almost free from any train interference.

DETENT. - A part that stops another part from operating at some point during a cycle. A locking device. The most common types of detents include those that stop movement in one direction only, or in both directions.

DETENT ESCAPEMENT. - A detached escapement that features a jewel in a detent. The escape wheel locks when it contacts the jewel. Impulse is sent by the teeth of the wheel to a pallet located on the balance staff on every alternate swing. The detent is usually a pivoted lever or blade spring. This is the most delicate escapement used in portable timepieces and provides the best accuracy.

DIFFERENTIAL DIAL. - This type of dial features a revolving disc in the center. The dial is numbered from I to XII. The revolving disc rotates 13/12 of a full circle every hour. The minute hand revolves around the face once per hour, always passing over the current hour. Some of these were made around 1700, but it is easier to find later samples.

DIVIDED LIFT. - A divided lift occurs when the impulse angles are divided between the impulse faces on the pallets and the escape wheel teeth. It is found in Swiss and French club-toothed escape wheel systems. English watches using lever escapements are do not have divided lift.

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DOME. - In the late 1800s, the double bottomed watch case changed. The dome was an inner cover in these later cases. Domes featured hinges so they could be opened easily.

DOUBLE-BOTTOM CASE. - A watch casing in which the inner section is a single piece with the case band. The movement of the watch is attached by a joint and bolt to the case. When the bezel is open and the bolt is pushed back, the movement can be hinged out of the case. It is common to have two holes to wind the watch and manually set the hands in the double bottom; it is hidden until the back is opened up. Very popular in the early to mid-1800s. See consular case.

DOUBLE ROLLER. - A type of lever escapement that uses a second roller for guard action.

DRAW. - A small recoil action in a lever escapement that occurs during the unlocking portion of the cycle. The draw makes sure that the lever is drawn to the banking pins as the balance traverses its supplementary arc. Think of it as a safety action that prevents the tendency for the lever to leave the banking pins before being moved away by the impulse pin. Escapements without draw may cause the lever to jolt away from the pins, creating friction when the guard pin contacts the edge of the roller. Good draw is accomplished by the angles between the teeth of the escape wheel and the locking faces on the pallet stones. The pressure caused by the tooth against the locking face of the pallet produces the drawing motion of the pallet towards the wheel.

DROP. - The free movement of the escape wheel in the time between the impulse and locking in place.

DUMB-REPEATER. - A repeating watch in which the hammers that strike the hours and quarters hit the case or a block inside the case instead of a bell or gong. Introduced around 1750 by Julien Le Roy.

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DUPLEX-ESCAPEMENT. - Two different escapements fit this term. One with two wheels located on the same arbor and more frequently, one with an escape wheel with two separate sets of teeth; one for sending impulse and one for locking. Classified as a frictional rest, single-beat escapement. The escape wheel lock has long, pointed teeth on the periphery rest against a hollowed ruby cylinder fitted with the balance staff. The cylinder stops the teeth as they cross paths. A notch is cut in the cylinder that allows a tooth to pass when the balance swings in the opposite direction. When a tooth is unlocked, a long piece attached to the balance staff gets an impulse from a shorter tooth that stands up on the face of the wheel. Once the impulse is complete, the next long tooth drops into place on the roller while the balance finishes its supplementary arc. On its return, the tooth catches in the notch. Impulses are in a single direction only; when the balance and escape wheel are headed in opposite directions. This escapement was designed by Jean-Baptiste Dutertre in the early 1700s, then adapted by Pierre Le Roy. It was finally patented in England in 1782, number 1311 by Thomas Tyrer. The duplex escapement was very popular in England for high quality watches in the early 1800s.

DUST-CAP. - A cap placed over the movement of pair-cased watches to keep out dust. This was seen on watches that were hinged to the case. Dust-caps became popular around 1715 in England. They were usually made of brass, though once in awhile a silver one can be found.

DUTCH FORGERIES. - During the second have of the 18th century, a large number of inferior watches were exported to England, Holland, Germany and many other countries purporting to be made by English companies. Many were marked with English names and some included forged English hallmarks. Because many of these watches used dials which were popular in Holland, it was originally thought they were Dutch. In reality, they came from the city of Geneva. The issue is further complicated by the popular painted enamel dials made in Geneva were frequently used on genuine English watches, as well as Swiss movements being placed in English cases in Holland. The forged watches are recognized by inferior workmanship, the use of a bridge rather than a balance cock, an arcaded minute band on the dial and a strange maker’s name without a Christian name or initial.

EBAUCHE. - A movement blank, only roughly cut in an incomplete stage of creation. In the early 1800s, this included two plates with bars and pillars, a barrel, an index, assembly screws, a click and a ratchet wheel. The parts were only roughly milled. Lancashire became the hub of the movement trade in the 1800s.

END SHAKE. - The clearance necessary between the shoulders or ends of an arbor and the bearing surfaces. Axial play.

END STONE. - A small disk made of low grade or synthetic jewel for a watch pivot to rest. Used especially for the balance staff pivot. Usually fixed to the balance cock with screws. Continental watches had a polishes steel plate as the end plate. Also called cap jewels.

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ENDLESS SCREW. - A tangent screw or worm.

ENGINE TURNING. - Patterns put on a metal surface for decoration using an engine turning lathe. Also called guilloche. A popular method of watch case decoration starting around 1770. Frequently used with translucent enamels.

ENGLISH LEVER ESCAPEMENT. - In this lever escapement, the escape wheel has pointed teeth. The impulse is centred entirely on the pallet stones and the lift is accomplished by on the pallets. See lever escapement.

ENTRY PALLET. - The pallet that receives the impulses from the teeth of the escape wheel as they enter. Also called the receiving pallet.

EQUATION OF TIME. - A mathematical equation first worked out by John Flamsteed around 1670 by calculating the difference between true solar noon and noon mean time. The mean time is the average length of every solar day in the year. The appropriate number is added or subtracted from true solar time to get mean time.

ESCAPEMENT. - The part of a watch movement that controls the release of motion and energy to the balance to keep it oscillating in a regular pattern. The balance and spring control the regularity of this motion in order to keep time. Escapements come in many designs:

  1. Frictional rests keep the balance in constant contact with a portion of the escapement.
    • Recoil escapements cause a recoil of the escape wheel through the use of eccentric locking faces. A verge escapement is of this type.
    • Dead-beat escapements that have no recoil and use concentric locking faces. A cylinder escapement is of this type.
  2. Detached escapements that feature a balance that is detached from the escapement except when locking or receiving impulses. A lever escapement is of this type.
  3. Single beat escapements only provide a single impulse for every double swing the balance makes. Duplex and chronometer detent escapements of of this type.
  4. Constant force escapements use a remontoire, or intermediate spring, that is wound every so often by the train. This spring sends impulses to the balance.

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ESCAPE WHEEL. - This wheel is the last one in the going train, which allows the escape of the energy causing motion to the balance. It locks and releases in an alternate pattern.

EXIT PALLET. - The pallet that receives the impulses from the teeth of the escape wheel as they leave. Also called the discharging pallet.

FALSE PENDULUM. - Also known as a mock pendulum. Popular around 1700, especially in Holland. The movement of a small disc mounted on one arm of the balance appears through an aperture, creating the appearance of a pendulum.

FIGURE PLATE. - Could not find a description of this part.

FIVE-MINUTE REPEATER. - A repeating watch that calls the hours and announces each five minutes after the hour. Some of these watches also marked the quarters. They are fairly rare, with many being made in the mid- to late 1700s, and a few more in the late 1800s. They first appeared around 1710.

FLAGS. - The pallets found in a verge escapement.

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FLIRT. - A device, such as a lever, that causes a sudden movement of a mechanism.

FLOATING HOUR DIAL. - Also called a wandering hour dial or chronoscope. Roman numerals appear in a semi-circular slit in the upper portion of the dial, one at a time, in succession. Minutes are marked on the outer edge, marked from 0 to 60. The hour numeral moves from left to right, indicating how many minutes have passed within that hour. When 60 minutes has been reached, the Roman numeral is replaced by the next in line. An inner semi-circle is marked in quarter hours. These watches were very popular in the last part of the 1600s and the early 1700s. A small amount were produced in the late 1800s and early 1900s.

FLY. - A fan with two blades that acts as a braking system to regulate the speed of repeating or striking.

FLY-BACK HAND. - Found in split-seconds chronographs, a fly-back hand is a second hand located in the centre of the dial that can move while staying superimposed on the first hand. The second hand can be stopped independently, and then it can fly back to rejoin the first hand.

FOB CHAIN. - A chain or ribbon used to attach a pocket watch. It usually hangs outside the pocket. The watch is attached to it using a bolt ring or swivel.

FOLIOT. - First used in clocks to control the escapement, the foliot is a cross bar with weighted ends like a dumb bell. It is positioned at the upper end of the verge. Foliots are usually found in early German stackfreed watches. By 1600, they were replaced by a plain balance or two arm ring.

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FORGERIES. - Watch forgeries were common in the early 1700s and again in the early 1800s. Famous makers like Quare, Graham, Tompion and Breguet were most commonly victimized.

FORK. - The end of the lever in a lever escapement that is shaped like a fork. The notch is located here.

FOURTH WHEEL. - This wheel drives the pinion in the escape wheel to the arbor where the second hand is affixed.

FORM WATCH. - A watch whose case is made in a different shape, such as a cross, star, musical instrument, and so on. They were most popular in the early 1600s, then again in the 1800s.

FOUR-COLOURED GOLD. - Gold that has been tinted using various alloys, turning the gold green, red, silver or yellow to be used in a decorative fashion. Also called tinted or coloured gold.

FRAME. - The movement plates.

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FREE-SPRUNG. - A balance spring without curb pins. Commonly used in high grade watches, pocket chronometers and marine chronometers. Timing screws on the balance can be adjusted.

FRICTIONAL REST ESCAPEMENT. - Verge, duplex and cylinder escapements are frictional rest variations. The balance is never free of the escapement in these designs.

FULL PLATE. - A calibre with a top plate and pillar plate that are circular in shape, and has the balance attached above the top plate.

FUSEE. - A truncated cone with spiral grooves up its length that holds the great wheel. It is a mainspring equalizer. First a length of gut, then after 1670, a chain, connects the mainspring barrel to the fusee. The fusee arbor can take the winding key. Winding draws the chain onto the fusee, taking it up the spiral. As the chain is removed from the barrel, the spring is wound. When fully wound, the mainspring has a larger torque to use. As the watch unwinds, the chain is taken from the narrow tip of the fusee first, where it has less leverage. This equalizes the repeater pull from the mainspring. More leverage is given as the chain is removed from the bottom of the fusee, compensating for the lessening strength of the spring. This allows a constant force on the mechanism. Fusees evolved until the proper shape was developed. The top of the fusee has a stop fitted, so when the chain reaches the last groove, a lever is lifted against a cam that stops the mechanism. This mounting was decorative after 1650. Fusees first came into use between 1450 and 1470. A ‘going fusee’ is one maintaining power.

FUSEE CHAIN. - A steel chain used to wind around the fusee after 1670; before this time, a gut cord was used. Christchurch, a town in Hampshire, specialized in making fusee chains.

GADROONING. - A type of decoration used on the edges of watches in the late 1700s and early 1800s consisting of cast or hammered lobes that radiated out. They could be either straight or curved.

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GATE. - The decorative piece that covers the fusee stop. Also the piece located over the locking detent on the striking train.

GATHERING PALLET. - A finger on the rack-striking mechanism that makes one revolution for every stroke of the hour. It gathers one tooth of the rack.

GIMBALS SUSPENSION. - Used to maintain marine chronometers in a horizontal position no matter how the ship moves. Utilizes two independent concentric rings that turn freely around their axes. Said to have been invented by Girolamo Cardano (1501–1576).

GOING BARREL. - A cylindrical shaped box with a toothed wheel located on the outer edge. The box holds the mainspring, and the wheel is the great wheel. The box turns freely from its arbor. See barrel.

GOING FUSEE. - A fusee with maintaining power.

GOING TRAIN. - The wheels and pinions concerned with the timekeeping mechanism.

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GONGS. - A coiled wire used in place of a bell for repeating or striking watches. Thought to have been developed by Julien Le Roy (1686–1759).

GRANDE SONNERIE. - A watch designed to strike both hours and quarters at each quarter.

GREAT WHEEL. - The wheel located on the going barrel; the first wheel in the train.

GUARD PIN. - Also known as a dart. A safety device found in lever escapements located near the balance. It prevents the unlocking of the escape wheel unless the impulse pin releases it.

GUILLOCHE. - A decoration made on a metal surface made by an engine turning lathe. See engine turning.

HAIRSPRING. - The balance spring.

HALF PLATE. - In this type of movement, the balance, fourth wheel and escape wheel have separate cocks.

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HALF-QUARTER. - A repeater watch that not only repeats the hours and quarters, but adds an additional stroke if seven or more minutes have passed since the last quarter. This feature was introduced around 1695.

HALLMARK. - A mark made using punches on gold or silver to identify the maker, quality of metal, the mark of the Hall and the standard mark. Some countries add assay marks.

HAND-SETTING. - Also known as the set-hand mechanism. This mechanism lets the hand positions be altered. Early watches had to be set by pushing the hour hand to the right hour. In two hand watches, a key was used on the hand-set square, otherwise known as the arbor supporting the hands. When keyless work was developed, the hands could be set using the winding button. See motion work.

HANGING BARREL. - Also known as a standing barrel, this is a going barrel attached to the movement by its upper portion beneath a cock or bridge.

HEART PIECE. - A cam shaped like a heart used in a chronograph that causes the chronograph hand to return to zero. First patented in 1844 by A. Nicole, patent #10348.

HELICAL SPRING. - Also known as a balance spring. Both Christiaan Huygens and Robert Hooke have been given credit with the invention of the balance spring, used to control watch mechanisms.

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HOG’S BRISTLE. - A flexible hair or bristle. Used in early German watches as a banking pivot. See bristle.

HOOKE’S LAW. - This law illustrates the elasticity of spring extension when a load is applied to it. It is written as F=-kx. x represents the displacement of the end of the spring from its position of equilibrium. F represents the restoring force that the spring exerts on that end, and k represents a constant known as spring constant or rate.

HORIZONTAL ESCAPEMENT. - Also known as a cylinder escapement, which is the more common name for this design.

HORNS. - The term for the horn shaped end of the fork found in the lever escapement. Each prong extends on one side of the notch.

HOUR RACK. - In 1676, Edward Barlow invented rack striking, a mechanism that determined how many strikes would occur for each hour. The hour rack is part of this mechanism; it moves one tooth per hour. The rack has a tail that drops onto the snail. Its position determines how many teeth are selected by the gathering pallet, which determines the number of hours struck.

HOUR WHEEL. - The wheel that carries the hour hand.

HUNTER. - A watch with a front and back cover, which protects the glass. A push-piece opens the front. A half-hunter has thick glass placed into the front cover so the dial can be seen.

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IMPULSE. - The energy received from the mainspring from the train and escapement that is transmitted to the balance to keep it moving back and forth.

IMPULSE ANGLE. - The angle that the lever moves through between the first contact of the escape wheel tooth on the impulse face and the last contact.

IMPULSE PALLET. - The pallet that receives the impulse energy.

IMPULSE PIN. - Also called a ruby pin. The impulse pin is attached into the roller and works inside the notch of the fork. When it enters the notch, it unlocks the escape wheel. It receives an impulse from the lever, which it passes to the opposite side of the fork. Usually made of ruby or sapphire (now synthetic). The impulse pin can be semi-circular, elliptical, triangular or half-moon shaped.

INDEPENDENT SECONDS. - A watch that has a second hand that is driven by a separate train. Credit is given to J. M. Pouzait, who developed this design in 1776. The second hand can be stopped without any interference with the regular functions of the watch.

INDEX. - The regulator. This is a small lever whose shorter end features the curb pins and whose longer end serves as an indicator as it passes over a scale of any changes made in the position of the curb pins. Regulation of the watch can be changed by moving the index towards S or R (slow or retard) or F or A (fast or avant).

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ISOCHRONOUS. - Occurs in equal lengths of time. The balance in a watch would be isochronous if the time taken for its oscillations were the same, no matter if the arcs were short or long. However, the arcs are affected by many things, like the position of the balance, and the impulses that are sent by the escapement. Keeping time accurately depends on the isochronism of the balance oscillations. Factors that may hinder isochronism include the escapement, the amount of play given to the balance spring between the curb pins, the spring, and faulty positioning of the balance.

JACQUEMART. - Also known as Jack. This is the automaton which strikes a bell (or appears to do so) at the hour or quarters. In watches, this refers to repeating watches that have figures appear to strike bells, but in reality, the normal mechanisms inside the watch cause the sounds that mark the time. These watches were very popular in Switzerland and France during the early 1800s.

JEWELS. - Watch movement bearings made from garnet, ruby, crystal or sapphire. Modern watches use synthetic jewels. Jewels reduce friction and keep the oil in place. The types of watch jewels include flat jewel holes, which are pierced with a cylindrical hole to take a shouldered pivot, domed jewels with endstones, which allow the tip of a pivot to rest on the endstone, and pallet stones. Sometimes a jewel can be found in the cylinder shell of a cylinder escapement. In this instance, the cylinder is called a ruby cylinder.

JUMP-HOUR. - This type of hour hand jumps forward at the hour, rather than moving slowly towards the next numeral. This type was used by Breguet for his repeating watches.

JUMPING-HOURS. - Hour numerals that are only visible through an aperture, then change each hour. This style was made in the early 1800s on the continent, then revived before World War II.

JUMPING-SECONDS. - A second hand which completes a single revolution on a subsidiary dial every second, or in four to five second jumps.

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KARRUSEL. - Invented by Bonniksen and patented in 1894 in England, this type of watch incorporates a method to eliminate rate errors in the vertical position. In this type of watch, the escapement is placed inside a cage or carriage, which is driven by the third wheel pinion. It revolves once every 52 minutes.

KEYLESS WATCH. - A watch that does not need a key to set the hand or to wind the mechanism. The keyless mechanism was perfected at the end of the 1800s.

KEYLESS WINDING. - A watch that does not need a key to wind the mechanism. Several systems were developed during the 1800s.

LEPINE CALIBRE. - Introduced in 1770 by J. A. Lepine, this movement features a design in which the top plate has been replaced by bridges or bars. This allows the watch to much thinner, even with a hanging going barrel and countersinks in the dial plate.

LEVER ESCAPEMENT. - An escapement that uses a lever to impart the impulse to the balance. At one end of the lever a pair of pallets can be found. The pallets engage with the escape wheel teeth, while at the other end, a notched fork receives the impulse pin, which is on a roller that is fixed to the balance staff. Lever escapements were divided into the English version, which had pointed teeth on the escape wheel, and the Swiss or continental version, with club teeth. English versions have the lift on the pallets, while the continental versions have the lift divided between the teeth and the pallets, although the action is basically the same.

LEVER NOTCH. - The opening in the fork end of the lever escapement in which the impulse pin enters.

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LIFT. - In a lever escapement, the angle through which the lever travels between the impulse and escape. Lift can be based all on the pallets, all on the teeth, or divided between the two.

LIGNE. - Also known as line. A unit of measurement indicating the size of a movement used in Swiss and French units. A ligne equals 2 X 25 mm.

LOCK(ING). - The time between impulses when the train is locked while the balance completes its supplementary arc in either direction.

LOCKING PLATE. - Also known as the count wheel. This wheel controls the number struck each hour. It is part of the striking train. See count wheel.

LUNETTE. - A rounded watch glass with a slight dome.

MAINSPRING. - The spring that creates the driving energy for the striking or going sides of a watch movement.

MAINTAINING POWER. - The device that drives a fusee movement using a ratchet and click during winding, when the power is otherwise taken away.

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MALTESE CROSS. - Associated with the Geneva stop-work; a wheel in the shape of a Maltese cross that forms part of a stop-work.

MARINE CHRONOMETER. - Also called a detent escapement. A detached escapement that has the escape wheel locked on a jewel attached in a detent. The most delicate and accurate escapement used in portable timepieces.

MASSEY LEVER ESCAPEMENT. - Designed by Edward Massey in 1814, this detached escapement is also known as a crank lever escapement. See crank lever escapement.

MEAN TIME. - The time kept by a watch; the average made from all the solar days of the year.

MIDDLE TEMPERATURE ERROR. - The compensatory effects of the bimetallic balance does not match the elasticity of the balance spring variables with a change in temperature. A watch with this type of balance will only be truly accurate in its rate for two temperatures. The inaccuracy between these two extremes can use auxiliary compensation to correct it.

MINUTE REPEATER. - A watch that repeats the hours, the quarters and the minutes that have elapsed since the last quarter. Very few of these were made in the late 1700s; they became more common at the end of the 1800s.

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MOCK PENDULUM. - Also known as a false pendulum. A small disc mounted on one arm of the balance is visible through an aperture as the balance moves, resulting the the appearance of a pendulum.

MOON HAND. - Also known as Breguet hands. The hour and minute hands were slightly tapered, with a disc near the end pierced to form a crescent.

MOTION WORK. - The gears beneath the dial which make the hour hand travel twelve times slower than the minute hand. This mechanism consists of a cannon pinion, a minute wheel and the pinion and hour wheel.

MOVEMENT. - The works of the watch sans the case, dial and hands. It consists of the escapement, power, transmission, regulating, and the mechanisms for winding and hand setting. See ebauche.

MUSICAL WATCH. - Produced in Switzerland in the late 1700s, these watches had a separate mechanism that could be set in motion on the hour or at will that produced a musical tune using a steel comb on a pinned barrel. Before the comb was developed, a set of bells was used to produce the music.

NIELLO. - Similar to champleve enamel, niello uses a black metallic filling of sulphur, lead and silver to fill a small area for decoration.

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NOTCH. - Also called lever notch. The opening in the fork end of a lever that takes in the impulse pin.

NUREMBERG EGG. - A name given to early South German watches due to an error in translation. The watches were drum-shaped or spherical, not egg-shaped. The mistranslation turned Uhrlein into Eierlein; literally ‘little watch’ into ‘little egg.’

OIL SINK. - A small cavity formed in the outside surface of movement plates surrounding the pivot holes to hold oil. Introduced around 1715 by Henry Sully. Later, jewels were made with oil sinks to retain the oil.

OIGNON. - The common name given to the bulbous, large French watches popular in the late 1600s and early 1700s.

OPENFACE. - A watch without a front cover.

ORMSKIRK. - The town in Lancashire, England, that became well-known for making watches using the Debaufre escapement. Watches made here are known as Ormskirk watches. See Debaufre escapement and dead-beat verge.

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OUTER CASE. - On pair-case watches, this refers to the outside case. They were often decorated.

OVERCOIL. - The last coil found in a Breguet balance spring. See balance spring.

PAIR-CASE. - The standard casing from 1650 to 1800 and beyond for English watches. Pair-cases were also used widely on the continent during the earlier period. The inner case houses the movement; it is usually plain unless the watch is a striking, alarm or repeater, when it is sometimes given minor decoration or pierced. The outer case is usually decorated with engraving, repousse, enamel or hollowed agate or other stone, according to the fashion of the period. Near the end of this time period, plain outer cases were more common.

PALLET. - The part or parts that receive and pass the impulse from the teeth of the escape wheel to the balance. Generally, pallets are jewels, and may be called pallet stones.

PARACHUTE. - Invented by Abraham Louis Breguet, the parachute is a device in which the balance staff endstones are supported in small arms of spring steel. Also known as sprung jewels. This gives a cushioning effect to the staff pivots in case the watch is dropped. Also called suspension elastique.

PASSING CRESCENT. - The hollow cut in the roller of a lever escapement that lets the guard pin pass. This cut is crescent-shaped.

PASSING SPRING. - Usually made of gold, this is also known as the gold spring. This is mounted on a detent in a chronometer escapement. The locked tooth is unlocked by the discharging pallet on the staff in one direction only. On the return swing, it passes by the detent without disturbing it because of the spring’s flexibility.

PEDOMETER WATCH. - Usually describes a watch and pedometer combined. The patent for this design was taken in 1700 by Ralph Gout.

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PEDOMETER-WIND. - Also called a perpetual watch. The watch is wound by the movement of a pivoted weight when the wearer moves normally. Invented by A. L. Perrelet around 1770. Many of these were made by Breguet.

PENDANT. - A neck fitted into a watch case where the bow is affixed. In keyless watches, the winding button is found at the top of the pendant, with the winding stem passing through the pendant.

PENDULUM WATCH (DIAL). - A watch which displays a mock or false pendulum through an aperture in the dial. It may also be visible through a slot in the bridge or balance cock.

PERPETUAL CALENDAR. - A watch with a calendar feature that does not require manual adjustment to deal with short months and leap years.

PERPETUAL WATCH. - Also known as a pedometer-wind. Perpetual watches wound themselves through the movement of a pivoted weight while the wearer moved normally. First made in 1770 by A. L. Perrelet. Patent number 1249 was taken on this design in 1780 by Recordon.

PILLARS. - These are the pieces which keep the plates in their positions. Early watches had square pillars; later, they were spiral or round balusters. Many shapes were used around 1600, including vase, tulip, lyre, pyramid and many others. Also known as distance pieces.

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PILLARPLATE. - The plate closest to the dial that holds the pillars. The pillars are only pinned to the top plate, which is furthest from the dial.

PINION. - A small wheel with teeth. The teeth may be called leaves. The wheel is the driver, while the pinion is the follower, with the exception of in the motion work.

PINCHBECK. - Named after its inventor, Christopher Pinchbeck, who in 1730 created this alloy of copper and zinc. It resembles gold. The term is also used for gilded brass.

PIN WORK. - Also called pique. Pins made of brass, gold or silver which secures leather, tortoiseshell or shagreen covering to the outer case of a watch. It was also decorative, as the pin heads could be arranged in an attractive pattern.

PIQUE. - Also called pin work. Pins made of silver, brass or gold were used to secure coverings made of tortoiseshell, leather or shagreen to the outer case of a watch. These pins were also used to create decorative patterns.

PIROUETTE. - A balance staff utilizing an integral pinion to cause the balance to swing in a large arc.

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PIVOT. - The extremity found on a rotating arbor.

PIVOTED DETENT. - This part provides the same function as a blade spring. Used on early chronometers by John Arnold. Pivoted detents were more popular on the continent.

PLATES. - Flat discs that sandwich the wheels and pinions between them. They form the movement’s foundation.

POISE. - If a balance does not have a heavy point, it is in poise. If the balance’s equilibrium is not affected by position change.

POKER HAND. - A minute hand formed in the shape of a poker. Usually paired with a beetle hour hand.

POSITIONAL ERROR. - Changes in a watches rate due to changes in position; from horizontal to vertical.

POTENCE. - A hanging bracket that supports a pivot, especially the underslung bracket that supports the lower pivot of the balance staff found in full plate watches. Early verge examples were made with the verge pivoting between the balance cock and an extended potence between the movement plates. When flatter watches were desired, the potence and the crown wheel were reduced in size. A second extended block was added to the potence for the inner pivot of the crown wheel arbor, while the other pivot was carried in an endpiece at the edge of the potence plate. Later improvements by Julien Le Roy introduced an adjustable potence, which allowed the escapement to be adjusted without taking the movement apart.

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POTENCE PLATE. - Another name for the top plate, which is the plate where the potence is attached.

POUZAIT ESCAPEMENT. - Developed by J. M. Pouzait (1743–1793), this was possibly the first divided lift lever escapement. The escape wheel had thirty teeth that stood up from the wheel’s plane. The claw-like pallets were made of steel, and the notch sent the impulse to the balance by way of a steel impulse pin on the balance staff. The diameter of the balance is almost the same as the movement plate. The escapement beat seconds. Safety action was provided by an upright pin on one arm of the lever, which acted on the outside of a safety ring on the balance staff when moving in one direction, then passed through an opening in the ring when moving in the other direction, putting it inside the safety ring.

PUMP-WIND. - An early version of keyless winding. The watch was wound by moving a shaft found in the pendant using a pushing or pulling action. Several watchmakers were associated with pump-winding, including Edward Massey, Burdess, and Viner.

PULSE-PIECE. - Also called a deaf-piece or sourdine. This is a pin that projects from the edge of a repeating movement, through the bottom edge of the case. The wearer could hold a finger against the pin to prevent the hammer from striking the bell.

PURITAN WATCH. - A simple English watch, without decoration. Usually oval in shape and made of silver. This design was made between 1625 and 1650.

QUARTER RACK. - Part of the striking mechanism that allows the watch to strike the quarter hours. See hour rack.

QUARTER REPEATER. - A watch designed to repeat the quarters and hours when the wearer presses a push-piece or moves a slide-piece.

RACK. - A toothed segment found in the striking mechanism. See hour rack.

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RACK LEVER ESCAPEMENT. - A lever escapement featuring a lever that terminates in a rack, which meshes with the balance staff pinion. The balance is never detached. Patented in 1791 by Peter Litherland, an earlier version was made in 1722 by the Abbe de Hautefeuille. This escapement was made in large numbers in the early 1800s in Lancashire.

RACK STRIKING. - Part of the striking mechanism that allows the watch to strike the hours and quarters. See hour rack.

RATCHET WHEEL. - A wheel with saw teeth. The fronts of the teeth are radial, while the backs are straight lines. This type of wheel is used with a click and spring. It is fixed with a square hole to the barrel arbor. The click stops the wheel from turning in the wrong direction. A ratchet wheel was the first method to regulate fusee watches.

RATE. - A watches timekeeping performance. The term ‘daily rate’ is used to show the difference between two readings of a timepiece, taken 24 hours apart.

RECOIL. - The backward movement by the escape wheel when it unlocks. This occurs when a tooth of the escape wheel is pressed backward by the exit pallet. If the watch escapement has draw, the wheel recoils the moment unlocking occurs.

RECOIL ESCAPEMENT. - An escapement that utilizes recoil.

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REGULATION. - Watch regulation has changed greatly over the years. Before balance springs, regulation required an altering of the mainspring’s set up. In some early German watches, the supplementary arc could be adjusted by changing the position of the upright bristles that the arms of the balance (foliot) banked against. Alternatively, a long bristle could lay across the balance. The length of this bristle could be adjusted by flexing it against two upright pins as the balance swung back and forth.

Adjustable regulation was first performed with the ratchet and click, which was used on fusee watches until around 1640, when the tangent screw and wheel became popular. After balance springs were invented, the set up was transferred from the top plate to between the plates. The only way to regulate the watch was to alter the length of the spring. This was done almost universally using Tompion’s development of a segmental rack, which followed the outer coil of the spring. It was geared to a small wheel that carried an index dial and a key square. A key was needed to alter the curb pin positions so they either increased or decreased the length of the spring, causing the watch to gain or lose on its previous rate.

The index dial known as the rosette or figure plate provided a guide, though the numbers on it were arbitrary. Nathaniel Barrow provided the only other form of regulation during this period, consisting of a worm with a key square. The worm carried a slide that featured two curb pins that embraced the straightened outer end of the balance spring. The slide had a pointer, which moved across an index that was engraved on the movement plate. The index indicated the amount of movement necessary for proper regulation. Watches with this form of regulation are extremely rare today. A new slide was patented in 1755 by Joseph Bosley that had no wheel (the segmental rack). This slide had a small lever. The shorter end carried the curb pins, while the longer end traveled across a scale that would change the rate between fast and slow. Free-sprung watches can only be regulated by changing the timing screws located on the balance.

REGULATOR. - Also known as an index. A small lever that carries curb pins on its shorter end while the longer end moves over a scale that indicates the amount of alteration made to regulate the watch.

REMONTOIRE. - A spring or other mechanism that is wound by the train. It is discharged at regular intervals.

REMONTOIRE ESCAPEMENT. - An escapement that uses a remontoire between the balance and the escape wheel to make sure the balance gets constant force. The difference between a remontoire escapement and a remontoire is the point where the remontoire is introduced. In a remontoire escapement, the spring is used between the escape wheel and the balance, while in watches where only a remontoire is used, it is used between the mainspring and the escape wheel. Both provide a more consistent torque than can be delivered by the driving train. Also called a constant force escapement.

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REPEATER. - A repeating watch that allows the mechanism to be set in motion to mark the time by hammers striking a block, a gong or bells located within the watch case. Watches with a block for striking are known as dumb repeaters. Repeating work was developed by Daniel Quare between 1680 and 1686. The mechanism was improved by Matthew Stogden around 1725.

REPOUSSE. - The forming of a decoration by hammering metal from the back side into a pattern or shape that resulted in a relief forming on the front. Similar effects can be achieved by casting.

REPUBLICAN CALENDAR. - This calendar was introduced in France in 1792. It was used until January, 1806.

RESILIENT ESCAPEMENT. - A type of lever escapement that uses the impulse pin to press against the outside of the lever, making it yield so the pin can pass.

ROBIN ESCAPEMENT. - A single beat escapement introduced in the 1700s by a French watchmaker named Robin. The impulse is given by the escape wheel, which locks the lever. This is a rare escapement, though Breguet made several.

ROLLER. - Part of a lever escapement. A disc is fitted on the balance staff that carries the impulse pin. The balance staff receives the impulse from the pallets. A roller could refer to either a single or a table roller. Later lever escapements with double rollers had a smaller safety roller introduced with a crescent cut for the guard pin. In the duplex escapement, the roller is made into a hollow ruby cylinder that locks the teeth of the escape wheel. See table roller and crank lever escapement.

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ROSKOPF. - The first successful cheap watches were produced by G. T. Roskopf in 1867. The escapement was a basic lever, with steel pins used as the impulse pin and pallets. Today, this set up is called a pin lever.

RUBY CYLINDER ESCAPEMENT. - A cylinder escapement that used a cylinder shell made of ruby. Most likely made by John Arnold in 1764, but it didn’t get a lot of use for many years. Abraham Breguet used this escapement frequently.

RUN-TO-BANKING. - The movement of the lever in a lever escapement towards the banking pins once the tooth has provided impulse to the pallet. This step was introduced as a safety to make sure the escape wheel teeth passed through.

S BALANCE. - First used by John Arnold (1779–1782), this was an early version of a bimetallic compensation balance. The bimetallic strips were shaped into two long S pieces that were laminated. They moved inwards or outwards in response to hot or cold temperatures, shifting two weights positioned on opposite sides of the balance rim.

SAFETY ROLLER. - A small roller with a crescent-shaped hollow cut into it for the guard pin.

SAFETY DART. - Also known as the guard pin. A safety device used in the lever escapement. The dart would prevent the escape wheel from being unlocked except by the impulse pin.

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SAVAGE TWO-PIN. - Named after George Savage. A form of lever escapement that has the roller carrying two pins, which function to unlock the escapement by using the fork. Another pin, mounted in an upright position at the end of the lever, performs as the impulse pin, passing into a small notch in the roller after the escape wheel is unlocked. This third pin also doubles as the guard pin during the supplementary arc. This design was introduced about 1814. Very few watches made by George Savage have survived.

SAVONNETTE. - A watch made with a front cover to protect the crystal. See hunter.

SECONDS PINION. - An extension on the fourth wheel arbor that holds the second hand.

SECRET SIGNATURE. - Used by Abraham Breguet to fight the forging of his work. Each watch had the name and number of the watch engraved on the dial with a pantograph. These marks can only be seen when the dial has the light falling across it with close examination. Many makers after Breguet also used this to mark their work.

SECRET SPRING. - Found in a hunter watch case; the fly and lock springs.

SELF-COMPENSATING SPRING. - A balance spring manufactured from an alloy that is impervious to changes in temperature.

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SELF-WINDING. - Also known as a perpetual watch. The mechanism winds itself through the movement of the wearer’s arm during normal activities. See perpetual watch.

SET-UP. - This is the degree of tension on the mainspring when the watch has fully run down. A stop-work lets a going barrel watch to be set up so only the middle turns are used for the mainspring, which provides more torque. In the fusee, altering the set up, a degree of regulation was changed.

SHIP’S CHRONOMETER. - Also known as a detent escapement. This is the most accurate and delicate type of escapement used in portable timepieces. See detent escapement.

SINGLE ROLLER. - Also called a table roller. The roller in a lever escapement that carries the impulse pin.

SIX-HOUR DIAL. - From the late 1600s; this dial featured six Roman numerals from I through VI set equidistant around the dial, then superimposed the Arabic numerals 7 through 12 over the Roman numerals. The only hand makes a revolution once every six hours. Minutes were marked by twos.

SKELETON DIAL. - A dial designed with the metal cut away to expose the movement, leaving only the hour and minute ring.

SKELETONISED MOVEMENT. - A movement that has had all extra metal removed from the top movement plate to expose the wheel work.

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SNAIL. - A cam cut in the shape of a snail, found as part of the striking mechanism in a rack-striking system. Steps are cut into the snail, allowing it to determine how far the rack may fall when released, and how many blows are struck each hour.

SOUSCRIPTION (MONTRE A). - The most inexpensive Breguet watch which still maintains the highest quality. These watches were subscribed for in advance. Breguet made them in batches.

SPLIT-SECONDS. - A type of chronograph with two centre second hands, one located over the other. The hands travel together during normal use. Through the use of a push-piece, the bottom one can be stopped while the top continues. The hand that has been stopped can be made to rejoin the other, or the top second hand can be stopped. Another push places both hands at zero.

SPRING BARREL. - The barrel that holds the mainspring.

SPRING DETENT. - A blade in the chronometer escapement that carries the locking jewel. A detent attached on a spring. Sometimes known as a footed detent. John Arnold patented it in 1782.

STACKFREED. - An eccentric snail or cam that serves as a mainspring equalizer; fond mostly in German watches of the period. The stackfreed is mounted on a wheel that is geared to a pinion on the arbor of the mainspring. It revolves less than one full turn on one winding. A strong spring presses against the edge of the snail. The spring ends in a roller, which creates friction between the stackfreed wheel and the post which it revolves on. The friction will vary according to the radius of the snail. There is a section of the wheel upon which the snail is mounted without teeth. Along with the mainspring arbor pinion, this provides the stop-work. When the watch has run down, the roller rests in a notch of the snail, untensioned. When the watch is wound, the pinion touches the uncut portion of the snail wheel, which is the stop position. During winding, the roller is moved out of the notch to the highest portion of the snail, to exert the greatest pressure. As the watch works, the pressure decreases as the spring winds down. This stop-work helps prevent over-winding; it can also be adjusted to only use the middle portion of the mainspring to avoid the two extremes at either end of the spring. Probably invented in Nuremberg in the early 1500s, the stackfreed worked well when making thinner watches.

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STANDING BARREL. - Also known as a hanging barrel. A going barrel whose arbor is only supported at the upper end.

STOP-WORK. - A mechanism that prevents over-winding of the mainspring. See stackfreed.

STRAIGHT LINE LEVER. - A lever escapement with the balance staff, pallet staff and escape wheel arbor set in a straight line.

STRIP COMPENSATION. - Also known as a compensation curb. A laminated bar made of steel and brass at one end and swinging free at the other. The free end carries curb pins. First used by John Harrison, the strip would bend depending on the rise and fall of the temperature, to compensate for any possible inaccuracies in timekeeping. See compensation curb.

STUD. - A small metal piece pierced so it receives the end of the balance spring’s outer coil.

SUGAR TONGS. - A compensation curb designed by Thomas Earnshaw, which roughly resembles a pair of tongs.

SUN AND MOON DIAL. - Popular in the late 1600s and early 1700s, the dial has a sun on one half and a moon on the other. The disc revolves once every 24 hours, so each icon is visible through a semi-circular hole cut in the dial plate in turn. The sun shows from 6 a.m. to 6 p.m., and the moon shows from 6 p.m. to 6 a.m.

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SUPPLEMENTARY ARC. - The arc traveled by an oscillating balance after the impulse and before unlocking.

SURPRISE PIECE. - A mechanism attached to the quarter snail of a repeater that prevents incorrect striking just before the next hour.

SWEEP SECONDS. - Also called centre seconds. A second hand in the centre of the dial with the hour and minute hands. They circle the dial in one minute.

SWING WHEEL. - A previous name for the escape wheel.

SWISS LEVER ESCAPEMENT. - The lever escapement used today. It can be distinguished by its club-toothed escape wheel teeth.

TABLE ROLLER. - In a lever escapement, the roller that carries the impulse pin. It was originally called a table roller to distinguish it from the part in Massey’s escapement that carried the impulse pin. On a table roller, the impulse pin is a jewel that protrudes downward from the table, while in Massey’s escapement, the impulse pin protrudes from the circumference. The table roller was developed around 1825.

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TACT. - A watch with a hand on the back cover that could be moved with a finger. Once at the correct time, the hand would stop, enabling the wearer to read the time in the dark through the use of the hand and the pins that indicated the hour. Also called a montre a tact. This type of watch was an inexpensive version of a repeater. Many of these watches were made by Breguet.

TAILLE DOUCE. - Engraving made by many fine lines.

TAMBOUR CASE. - An early type of watch case that was shaped like a pill box with a hinged cover. It was made from cast brass and was often chiselled and engraved.

TANGENT SCREW. - An endless screw. Also called worm gear. Before the mid-1600s, the tangent screw and wheel were used instead of the ratchet wheel method to regulate and set the mainspring. The index was a small dial on the top plate. After 1675, the mechanism was set between the plates.

TEMPERATURE COMPENSATION. - Any mechanism that counteracts the effects of temperature change on a watch’s rate, especially on the steel balance spring, which tends to lose elasticity when the temperature rises and becomes too elastic when the temperature falls.

TERMINAL CURVES. - The curves found at each end of a helical or cylindrical balance spring. In order to be isochronal, the spring’s center of gravity should lie on the axis of the balance. The best way to achieve this is to attach the inner and outer ends in a set relationship to each other. Edouard Phillips investigated the geometry of the balance spring in 1858.

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THIRD WHEEL. - The wheel located between the centre and the fourth wheel.

THREE-QUARTER PLATE. - A calibre with a section of the top plate removed to mount the balance in the same plane as the plate. In this design, the escape wheel and the balance have separate cocks.

TIMING IN POSITIONS. - The ability to adjust the balance and the spring so the watch remains accurate no matter the position. See adjusted.

TIMING SCREWS. - The screws located at the ends of the arms of a compensated balance used to adjust the watch to time. There are two timing nuts or screws in a chronometer balance; one is located at each end of the arm. Not to be confused with balance screws, which are used to adjust the compensation.

TINTED GOLD. - Also called coloured gold. Used to decorate watch cases, dials and jewelry. Gold is colored by adding alloys to produce yellow, green, red or silver hues. Introduced in the last half of the 1700s. Sometimes combined with gemstones on cases.

TIPSY-KEY. - Also called a Breguet key. This key prevented winding the watch in the wrong direction.

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TOMPION REGULATOR. - A regulator made of a segmental rack that follows the outer spring coil. It is geared to a small wheel that is attached to an index dial and a key square. The key enabled the wearer to alter the curb pin locations to correct the rate of the watch. See regulation.

TOP PLATE. - The plate furthest from the dial. Also called the potence plate.

TOUCH PINS. - Pins located at the hour positions. This was a method used in the 1500s to enable the wearer to read the time in the dark.

TOURBILLON. - Invented by Abraham Louis Breguet and patented in 1801. A tourbillon eliminates the positional (vertical) errors that occur in a watch. To do so, the escapement is mounted inside a revolving cage or carriage. This carriage repeats the errors to cancel them out. In some watches, the escape wheel pinion revolves about the fixed fourth wheel and the carriage turns once per minute, while in others the revolution only occurs every four to six minutes.

TRAIN. - The pinions and wheels that connect the fusee or going barrel to the escapement. In watches, the wheel drives the train and the pinion follows, with the exception of motion work. The going train deals with timekeeping, while the striking train deals with marking the hours. In a fusee, the great wheel drives the centre pinion to the arbor, which is attached to the centre wheel. This drives the third wheel pinion, which in turn drives the fourth wheel pinion. In a going barrel, it is the teeth around the barrel which starts the motion.

TRIAL NUMBER. - This symbol is used to mark the excellence of watches and chronometers in competitive trials. In the Greenwich Observator method, the difference between the greatest and least variation was multiplied by twice the difference noted between one week and the next.

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TRIPLE-CASED. - A watch with an additional case added to a pair-case watch. Usually found in the Turkish market.

TRIPPING. - When two teeth on the escape wheel pass instead of one. Tripping can occur in detent and duplex escapements.

TURKISH MARKET WATCHES. - Watches made especially to export to Turkey. The dials were adorned with ‘Turkish’ numerals. They had three cases; a plain one over the movement, one with engraving and a third covered in tortoiseshell or shagreen. Sometimes a fourth case made of silver or leather is present. Watches were exported to Turkey in the 1600s, and by the end of the 1700s, many of these watches were made in London.

TWO-PIN ESCAPEMENT. - Also called a Savage two-pin. Named after George Savage. A form of lever escapement that features a roller carrying two pins to unlock the escapement via the fork. See Savage two-pin.

UNDER-DIAL WORK. - Additional mechanisms such as calendar, repeating and lunar located on the dial plate in addition to the motion work.

UP-AND-DOWN DIAL. - Usually found on marine chronometers or on pocket chronometers. Also found on some high quality watches between 1880 and 1910. A subsidiary dial that indicates the state of wind for the mainspring.

VERGE. - The spindle or rod which holds the foliot or balance. The verge carries two pallets.

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VERGE ESCAPEMENT. - Also known as the crown-wheel escapement. Used in the earliest watches. This escapement has a crown wheel, also known as the escape wheel, whose arbor carries a pinion that is driven by the train. The verge is a vertical arbor that sits at a right angle to the crown wheel with two pallets. The pallets are separated by a distance that about equals the diameter of the crown wheel, at an angle of about 100 degrees. A balance sits on the upper end of the verge. It is pivoted at its two extremes. The crown wheel’s teeth cause the balance to oscillate by alternately acting upon the pallets. The crown wheel has eleven or thirteen teeth. They are triangular in shape, while the wheel resembles a crown. Each tooth comes into contact with a pallet, gives an impulse, and gives motion to the balance. The wheel is then free to move forward, but almost instantly, a tooth from the opposite side of the wheel contacts the opposite pallet, and the motion repeats itself in the opposite direction. This is a recoil escapement. See recoil escapement.

VIRGULE ESCAPEMENT. - Also called a hook escapement. Both names come from the shape of the part that gets the impulse, which looks rather like a comma. It is similar to a cylinder escapement in that it is a frictional rest escapement. J. A. Lepaute is usually credited with its development in the late 1700s. It resembles a patent taken out in 1695 by Edward Booth and William Houghton.

WANDERING HOUR DIAL. - Also called a floating hour dial. The Roman hour numerals are revealed one at a time through a little semi-circular opening in the upper portion of the dial. Minute gradations are marked on the outer edge. The hour numeral travels from left to right, marking the number of minutes that have passed after the hour. When it reaches 60 minutes, it disappears so the next numeral can be shown. Another semi-circle is marked in quarter hours. These watches were popular in the last part of the 1600s, and there were also a few made in the late 1800s.

WARNING. - The preparation to strike that occurs a few minutes before a watch strikes the hour. A pin carried by the warning wheel in the striking train is stopped then released by the warning piece.

WATCH PAPER. - Made of embroidered muslin or cambric fabric or printed paper. This was placed in the back of the outer case in pair-case watches to prevent scratching of the inner case. It also took up any slack space. Later, advertisements were printed on this paper for the watchmaker or watch repair shop. Some also had rhymes or proverbs on them, while others presented the equation for time.

WINDING SQUARE. - A square end on a fusee arbor or barrel that takes a fitted key to wind the watch. A similar set up is on the arbor that holds the hands so they hands can be set.

WORM WHEEL. - Also referred to as worm gear, endless screw and tangent screw. This system replaced the ratchet wheel system to set the mainspring and regulate the rate of the watch. The worm wheel was mounted between the plates after 1675.

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