The serial number of a American Waltham Watch Company pocket watch is located on the movement of the watch. It can be found by removing the back case of the watch.
The serial number on a Waltham pocket watch is a good indicator of the year in which it was made. The company made watches from 1852 to 1957; so, for example, watches with serial numbers of less than 50 were made during the first year of manufacture while those with serial numbers between 34,700,000 to 35,000,000 were made in 1957.
The American Waltham Watch Company began in Massachusetts in 1850, with the aim of making quality watches using interchangeable components. The company's founders build a factory in 1851, after a number of initial experiments designing the watches and their parts.
Initially, the business was called American Horologe Company, and it was known by a number of names in subsequent years, including Boston Watch Company, Tracy, Baker and Co. and American Watch Company. In 1885, after a series of reorganizations and mergers, it became the American Waltham Watch Company.
In 1957, Waltham shifted its focus to making precision instruments instead of watches. The rights to the Waltham Watches name were sold to a company in Chicago, who sold imported timepieces under the Waltham brand.