When was your Seiko made?
Enter the serial engraved on the caseback. Add the caseback number — like 6309-7040 — and we’ll narrow the decade and show the matching watches from original Seiko catalogues.
Where do I find these numbers?
Both are engraved on the outside of the caseback — the metal back of the watch. The serial is usually six characters. The caseback number is the caliber and the case code joined by a hyphen, e.g. 6309-7040: the first half (6309) is the movement and narrows the decade; the second half (7040) is the case and identifies the model, so we list the matching watches from the original catalogues. The caliber alone works too.
Type a serial above — the reading appears here instantly, entirely in your browser.
How the code works
Year
The first character is the last digit of the production year — so it repeats every decade.
Month
The second character is the month: 1–9 for January–September, then O, N, D for October, November, December.
Sequence
The remaining digits are that month’s production count for the line.
Seiko has never published an official serial-dating standard — this is a community-derived convention. It works for most Seiko (and Seiko 5) watches from 1966 onward, but can mislead on Grand Seiko, some quartz lines, and watches with service-replaced movements. Treat the result as a strong estimate, not a certificate.