Pocketwatch 101™ – Learn about Vintage and Antique Pocket Watches
Vintage Watch Case Materials
How to tell if your vintage watch case is gold or gold-plated?
Solid Gold Watch Cases
If your vintage pocket watch is in a gold-colored case, odds are good that you have a gold-plated or gold-filled case. There were far more gold-filled cases made than solid-gold "karat cases"... in fact, only about 5% of cases made were solid gold. These days, solid-gold cases have become even more scarce because so many of the large gold cases have been scrapped for their gold-value (a practice we abhor and highly discourage, by the way). But there were some beautiful, solid-gold cases made over the years and many of them have survived intact. So if you have a vintage watch that's housed in a solid-gold case, consider yourself lucky!
It's important to understand the difference between "solid-gold" and "pure gold". Solid-gold means the case is gold all the way through. Pure gold (100%) with no other metals added is called 24-karat, but pure gold is much too soft to be useful as a metal for making jewelry or watch cases. Gold must be alloyed with other metals to make it hard enough to be usable. T purity of gold is expressed as a fraction of "pure" 24 karat gold... so if something is marked as 12-karat gold, that means it is 12/24ths or 50% gold. Gold coins are about 22K (91.6%), and the highest purity typically found in jewelry or watch cases is 18K (75%). Most solid-gold watch cases are 10K - 14K (41.6% and 58.3%, respectively).
If a watch case is solid-gold it will usually be hallmarked or stamped with a karat symbol or assay mark, like "WARRANTED U.S. ASSAY". Proper case-marks are usually a good indication of gold-content, but gold-testing is advised if you want to be sure. Markings on the case are sometimes ambiguous, and counterfeit or "upgraded" assay marks, while certainly not common, are known to exist. A good jeweler or goldsmith should be able to acid-test your case for gold-purity. Below are examples of markings on solid-gold watch cases.
Gold-Filled Watch Cases
James Boss, an early partner in the company that was to become the Keystone Watch Case Company, is credited with the development of the gold-filled watch case which was patented in 1859. Although James Boss certainly didn't invent the process of making rolled gold plate, Keystone "J. Boss" watch cases were the first widely adopted and commercially successful gold-filled watch cases, and are still commonly found on vintage watches today. If your Keystone case is marked "J. Boss" or "Jas. Boss" then it is a gold-filled case. After Keystone achieved success with gold-filled cases, many other case manufacturers began producing gold-filled cases.
Gold-filled cases were made by sandwiching together 2 bars of gold (typically about 1/2" thick) on either side of a bar of base-metal, often brass or brass-alloy (typically 3/4" thick). The 3 bars were soldered together under high pressure and high temperature in specially constructed ovens. The composite 3-layer bar was then rolled through high-pressure rolling mills until the desired thickness was reached. The gold layers could consist of 10-karat, 14-karat or 18-karat gold. While this process produced a thicker layer of gold than electro-plating, the gold content was still no more than 5-10% of the total case weight. As such, gold-filled watches do not have any significant gold value.
Gold-filled cases were often marked with a guarantee, another innovation credited to James Boss, which specified a number of years that the case was guaranteed to wear. A case that's marked "14K Warranted 20 Years" meant that the gold-filled case was made with a layer of 14K gold, and was guaranteed that the gold-layer would not wear through to the base-metal for a period of 20 years. If your case is marked "Warranted 20 Years" or "10 Year Guaranteed" or any other reference to a number of years or guarantee, then it is a gold-filled or gold-plated case. Note that the year-guarantee was related to the thickness of the gold layer, not to the karat-quality of the gold used in the gold layers. In general, a longer guarantee implied a thicker layer of gold. Most gold-filled cases were made with 10K or 14K gold.
The year-guarantee markings on cases continued until 1924, when the practice was prohibited by law due to the failure of some manufacturers to stand behind the so-called "guarantees" on their cases. This provides the vintage watch collector with an easy method of roughly dating a case: If it's marked "Guaranteed for x Years" you know that it was made prior to 1924. After 1924, gold-filled cases were simply marked "Gold-Filled" as seen below.
Silver Watch Cases
Silver was also a commonly-used case material, and some beautiful examples of silver cases may still be found today. Silver cases can be marked in a variety of ways: Sterling (.925 fine), Coin Silver (around .90 fine, made from melted US coinage), Fine Silver (.995). Below are examples of coin-silver case marks.
Nickel Alloy Cases
In addition to gold and gold-filled cases, manufacturers produced cases from many other materials as well. Nickel-alloy cases were produced under many names by American case manufacturers. Each manufacturer had their own unique name, and their own formulation, but cases were usually a mixture of Nickel (45%), Copper (54%) and Manganese (1%).
Manufacturers often chose names for their nickel-alloy cases which were suggestive of silver content, but none of the nickel-alloy cases actually contained any silver. Some common names were: Nickeloid, Nickel Silver (Illinois Watch Case Co.), Silverine (Dueber Watch Case Co.), Silverore (Fahys Watch Case Co.), Silvaloy, Silveroid (Keystone Watch Case Co..), Silveride, German Silver, Silverode (Philadelphia Watch Case Co.). Nickel-alloy cases are very durable, and many fine examples survive today.
Other Case Materials
There are examples of pocket watch cases made in platinum or rhodium, but these are extremely rare. Many materials have been used to produce "one-of-a-kind" watch cases, but the materials listed above comprise the vast majority of cases the collector is likely to encounter.