Dating a watch is an inexact science. It's virtually impossible to identify a watch down to the exact production date. The best way to identify the date of manufacture of a watch is to locate the serial number on the watch's movement. The movement is the spring-loaded mechanism the runs and regulates the timepiece. Comparing the number to the manufacturer's listings can date the manufacture to the approximate year. Watches like Elgin, Waltham and Omega kept excellent records, allowing for good dating of their watches. Watchmakers like Gruen, however, destroyed their records, making exact dating impossible.
Watches with Serial Numbers
Use a case blade to pry open the snap-on case back of a pocket or wristwatch. Rotate a screw-down case back counterclockwise with the palm of your hand. Remove the case back (of either type) from the watch.
Use a jeweler's loupe to inspect the movement for a serial number. Serial numbers can range from six to nine digits and may include a combination of letters and numbers. Elgins, for example, may have a letter in front of a series of numbers. Omegas have seven or eight digits. The serial numbers on an 1895 Omega pocket watch, for example, start at 1,000,000. A 1956 Omega wristwatch starts at 15,000,000.
Record the number. Check the number against the watchmaker's serial number lists. Watch enthusiast clubs post the serial numbers of major watchmakers online. Watchmakers specializing in vintage and contemporary mechanical watch repair also can obtain most lists.
Use a jeweler's loupe to examine the movement for a symbol. Some watchmakers, such as Bulova, used symbols instead of specific serial numbers to date their watches. A crescent moon, for example, identifies a 1928 Bulova. A triangle identifies a 1945 model.
Examine the exterior case back of a Bulova watch with the loupe for a single letter followed by two numbers. This designation began in the late 1940s. Bulova used "L" to designate 1950, "L1" for 1951, and so on. "M" followed for the 1960s and continued in alphabetical order with each decade. Very few watchmakers, however, stamped the year of manufacture on case backs.
Use the loupe to examine the inside of the case back for jeweler's marks. For most of the 19th and 20th century, watchmakers (in their role as repairpersons) etched the date of service inside the case back. A 50-year-old watch could have a dozen tiny dates etched inside. This not only gives you a service record of the watch, but it provides a clue to its era of manufacture in the first date the watch was serviced.
Visually inspect the watch dial, hands, case and case back to narrow the manufacturing date to a decade, if there are no serial numbers visible on the movement. Heavy fleur-de-lis engraving and skeleton watch hands denote 1920s vintage. Art Deco styling with sweeping, stepped geometric lines on rectangle cases with Lozenge-style hands characterize 1930s and 1940s timepieces. Watches from the 1950s feature round dials and dauphine or leaf-style hands. The 1960s often featured dials without numbers and with stick hands.