To look up the serial number of a vintage watch, visit an online watch collector site such as Antique Watch and Clock World. Many of these sites offer links to serial number tables for common watch brands.
Alternatively, visit Pocket Watch Database and enter your watch's serial number directly into the search tool. Select the watch's manufacturer and hit the search button to view your results.
Not all vintage watches have serial numbers. If they do not, the watch cannot be identified using this method. Most vintage Swiss pocket watches, for example, do not include serial numbers. However, numerous online watch collector sites offer extensive identification resources.