The pocket watch started out as a kind of miniature clock. Early watches were driven by internal springs. As the spring unwound, it supplied power to a series of gears that controlled the movement of the watch hands. With time, the pocket watch became increasingly elaborate. Ornate gold cases contained sophisticated movements complete with jewels, second hands and subsidiary dials. The various features of a pocket watch can help to identity its period of manufacture.
Open the pocket watch case. Cases with an obvious tab, or lip, will simply pull open. The lid screws off of some watch cases. In most other instances, use a case knife to carefully pry up the lid of the pocket watch case. The presence of very small hinges, and a tiny lip, typically indicates a pry-up case.
Look for the serial number that is engraved on the watch movement. The movement is the set of gears inside the pocket watch. Ignore numbers that appear on other parts of the watch. If the watch was manufactured by Bulova, the serial number will appear on the case itself. The name of the manufacturer will appear on the watch face.
Note any letters that follow the numbers in the serial number. Certain manufacturers used these letter codes as indications of the date of manufacture.
Compare the serial number to lists on pocket watch sites, such as The Watch Guy, and Antique Pocket Watch. Lists are also available for specific manufacturers, including Hamilton, Elgin and Waltham.
Identify watches without serial numbers by examining the style of the case. Nineteenth century watches are typically highly ornate and reflect the artistic tastes of the Empire, Regency or Victorian periods. Early 20th century watches often feature the dynamic geometric shapes of Art Deco or the more sinuous styles of Art Nouveau.
Look for jewels inside the movement. Jewels have been used as bearings inside English pocket watches since at least the early 18th century. Non-English watches did not use jewels until about a century later.
Letters in serial numbers typically denote a watch of somewhat later manufacture. Hamilton, for example, only began using letter codes in about 1940.
Do not force open the case of the pocket watch. If the watch is not opening, take it to a watch maker.