How to Date a Vintage Seiko Watch by Its Serial Number

Almost every vintage Seiko carries its birth date on the case back. You only need the serial number and a rough idea of when the model was made.

Find the serial number

Turn the watch over. On the case back you will see two sets of characters. The one in the format 0000-0000 is the movement and case code, for example 6309-7040. The other one, usually six digits (seven on some early models), is the serial number.

Read the first two characters

First digit: the last digit of the year. A 7 can mean 1967, 1977 or 1987.
Second character: the month. 1 to 9 are January to September, 0 is October, N is November and D is December.

The remaining digits are the production count for that month.

Work out the decade

The serial gives you only the last digit of the year, so the decade comes from the movement. Each Seiko calibre was produced for a limited period. The 6309 automatic, for example, was made from 1976 to 1988, so a 6309 with a serial starting 7 can be 1977 or 1987, and the dial and case style tell you which.

An example

A case back reads 4633-5029 with serial 770215. The first 7 is the year, the second 7 is July. The 4633 quartz calibre belongs to the 1970s, so the watch was made in July 1977.

What the serial cannot tell you

It dates the case back, not every part. Dials, hands and crystals are often changed during a long life, so compare the parts with period catalogue photos before paying a premium for an "all original" watch.