The Waltham Watch Company, which was based in Waltham, Mass., produced pocket and wrist watches between 1850 and 1957. Today, Waltham watches remain highly desirable collectable timepieces. Dating a Waltham is an easy task. The watchmaker kept thorough records of its products. Waltham etched a serial number on every watch movement along with its name and trademark. Unlike other watchmakers, Waltham went the extra step by usually identifying the model of the watch on the movement as well. This information can be used to find the year that the watch was made.
Use a flat blunt blade to pry open the snap case back of a Waltham wrist watch. A lip or notch on the case back can be found at the 6 or 12 o'clock position. If there is no lip, carefully wedge the blade into the seam and lift. The case should pop open.
Carefully examine the case back of a Waltham pocket watch. Pocket watch case backs vary in design and require different methods to open. For hinge back and bezel cases, examine the case back with a jeweller's loupe or the naked eye for two small hinges on the case back. The hinges are usually at the 6 o'clock position. Pry the case at the opposite end of the case back first with a fingernail. If that doesn't work use the flat blunt blade. The case should snap open. Hunting cases feature front and back covers. Press down on the crown and a tiny hatch will release the cover.
Use a jeweller's loupe to examine the movement. Don't touch the movement with your fingers. At or near the edge of the movement will be a serial number. Digits in the serial number will range from two to eight depending on the year of production. For example, 1856-1857 Waltham pocket watches will have a serial number between 4000 and 6000. A 1957 Waltham watch will have a serial number of 35,000,000 or greater, according to oldwatch.com. Record the serial number from the movement.
Use the jeweller's loupe to note the "American Watch Co. Waltham", "AWCO Waltham" or similar trademark. Note the number of jewels etched on the movement. Note and record the model name, such as "Riverside" or another model name on the movement.
Obtain a Waltham serial number list from the numerous online pocket watch sources or from an experienced watchmaker with an expertise in vintage watch identification and repair. The list will provide the year of production, but not the exact date.
Ignore the inside case back serial number. It provides no information. The inside case back should have the gold content embossed, such as 18k or lesser grade.
Never force open anything on a vintage pocket or wrist watch. If the case back doesn't open, have a professional watchmaker open it for you.