The Pocket Watch Case for the collector - Many Pocket Watch companies concentrated on just making the movements, leaving the case to be made by another company. There are lots of different types and grades of cases, some more valuable than others...
So first, the customer would choose the type of pocket watch they wanted, e.g., Waltham, Elgin, etc, then the particular grade, model and size, then decide what type of case they wanted the movement to live in. Now, pocket watches were never all that affordable until the availability of the so-called "dollar pocket watch", so people generally chose a relatively expensive case for their watch. Typical precious metals such as gold and silver were used.
For more practical purposes, a special alloy was developed which went by several different names, such as, "Silveroid, Silverore, Silverode or Silverine. "Silveroid" appears to have become the standard name for this metal that consisted of 45% nickel, 54% copper and 1% manganese. This metal was fairly hard wearing and could withstand the rigors of everyday use, for instance on the Railroads. For pocket watch collectors, almost all the value of the watch is in the movement. The case is really only of aesthetic value, although something made out of solid platinum or gold will always have an intrinsic value attached to it. Some people collect only pocket watch cases and I have seen this becoming more popular over the past few years as the price of movements increases.
The American case manufacturers used their trademarks on cases they made, hence you can tell from these marks and a few reference check from trademark books what the metal is. For European pocket watch cases, since the early 1600s, all solid precious metals were hallmarked. This makes it easy to tell what the case is and more importantly, what quality (or Karat) the metal is.
Gold filled needs some explanation. Put simply, this was a process where two bars of gold were sandwiched around a base metal (such as brass), then the sandwich was rolled until the desired thickness was achieved. This resulted in a gold plating that was generally thicker and hence more hard wearing than that of plating.
Gold filled cases almost all show a small amout of "brassing", that is the gold plating has worn off and the brass underneath is showing through, not surprising on a 100 year old case! You may see on some cases the word "Guaranteed" (see left) or "Warranted". This is the manufacturers guarantee of quality and is an indication that the gold filled case will last at least as long as the guarantee before the fill wears through. The higher years, the better the quality.
So as far as pocket watch cases go, buy what you like. My favorite is solid gold or platinum, they are expensive but do have an intinsic value attached to them and are generaly more pleasing to the eye (my opinion only)! My second choice would always be Silveroid cases, they are hard wearing, look great and don't wear like the gold filled variety.
Since I wrote this article, some 6 years ago, the price of Precious Metals have soared and so my choice of pocket watch case back then seems a pretty good investment. The problem now (2012) is that really good quality solid gold cases are fetching less than the price of the metal they are made of. If Gold and Platinum continue to increase in value against the US Dollar (and I expect they will as the US prints more and more dollars), cases will unfortunately be melted down purely for their metal value. This ultimately means that they will get even more scarce, and when the current crisis is resolved, I expect their prices to continue to increase substantially.