Seiko serial number

The serial on the caseback (six characters, seven on 1960s watches) gives the month and the last digit of the year. The decade has to come from somewhere else, so you get candidates.

We narrow the decade for calibers with known production years (6139, 6309, 7S26, 6R15, 4R36) – those years come from collector databases, are approximate and never rule a reading out. For other calibers you get every decade. The serial is usually next to the caliber–case number on the back.

Decoded in your browser. What you type isn’t sent anywhere or saved.

Waiting for a code

Enter a code to see what it says.

Everything is decoded in your browser. Nothing you type is sent anywhere or added to the page address.

Not proof of authenticity. The serial belongs to the caseback, and counterfeits copy real serials. Seiko publishes no table – this is a summary of what collectors observe.

checkthepiece.com/seiko

Check the whole watch with Legit Check Our photo-based app · iPhone

How to read a Seiko serial

On most Seiko watches since the late 1960s the serial has six characters. The first is the last digit of the year. The second is the month: 1–9 for January to September, 0 for October, N for November and D for December. The rest is a production number.

Because only one digit of the year is there, a 5 can mean 1975, 1985, 2005 or any other year ending in 5. The caliber (the first four characters of the caliber–case number, like 6139 in 6139-6000) narrows it, since each movement was made for a limited span – though many stayed in production for over ten years.

Seven-character serials belong to the 1960s. On some early-1960s pieces the month comes first.

What the serial can’t tell you

The decade, on its own.
Whether the watch is genuine – Seiko offers no public check and keeps no public serial database.
The retail model (like SRPD55): the caliber–case number is what identifies the type.
A date for the Seiko 5 Sports line relaunched in 2019, or for limited editions numbered like 0816/3500.

Genuine watches that confuse decoders

October written as 0. Some guides say the letter O, but we found no real serial with the letter O. We accept both.
Grand Seiko serials with a letter in the third place.
Serials that look earlier than the caliber’s announced start: production can run ahead of the announcement.
Dial date codes that differ from the serial by a month or two.
A service mark like B0206 on quartz divers is a battery change, not a production date.