Seiko watches have a 6 or 7 character serial number on their casebacks. The second character can be a letter but the rest are all numbers. You can use the Seiko serial number in conjunction with the movement number to calculate the year of manufacture. The month and last digit of the Seiko'a date of manufacture is calculated using the serial number and then narrowed down to a decade using my database of Seiko movement manufacture dates. You will be given an eBay link to check the value, useful links such as manuals, etc and for quartz models the battery information.

If more than one date is returned then either I lack data for that Seiko movement or it was made for over a decade. For details of my Seiko movements list click here. For information about how this actually decodes and how to decode a Seiko serial yourself click here (also has a video showing how to find your serial number and movement).

To get the best chance of getting only one date returned it is best to enter your Seiko movement in the 2nd box. The boxes are not case sensitive. The movement can contain the letter S, which can look very similar to a 5.

Please note, the new Seiko 5 sports cannot be dated by serial number. If you have a 2019 or newer Seiko 5 sports, then the 6 digit serial is actually a production number and cannot be used for dating purposes.