Date a Seiko by serial number
How to decode the serial number on a Seiko watch
The easiest way to find the date of a Seiko serial number is to use the automated Seiko serial number decoder
but this page explains how to do it manually.
Seiko watches use a 6 or 7 digit serial number stamped on the caseback. This serial number contains digits indicating the date. The first digit translates to the year and the second shows the month. As only 1 digit is used for the year this will only show you the last digit of the year, the decade cannot be found from the serial number, more on this later.
For the second digit 1-9 covers up to September. The letters O, N and D are used to represent October, November and December.
So the serial number 456789 could be May 1974, May 1984, May 1994, May 2004 etc.. There are visual clues as to which decade the watch may be from but the easiest way is by using the Seiko movement number, if you can find the date range for the particular Seiko movement you are likely to be able to pinpoint the exact date. This is how this tool works, I have collated the manufacture dates for as many Seiko movements as I could find which this tool uses along with the date code from the serial number. As some Seiko movements were made for more than a decade you may end up with a couple of possibilities.
Here is a video to help you locate the serial number and movement code on a few styles of Seiko watches :-
Seiko switched from a 7 digit serial number to a 6 digit serial number in 1968 and started switching from the wording "waterproof" to "water resist" from 1968 to 1971, both of these are automatically taken into account with my tool.
Additionally the case construction mark can be used to narrow the date down as it changed to one or two characters with a box around them in 1976. If you have characters in a box on the back of your Seiko it is 1976 or later. A lack of box does not help narrow it down as some watches do not have the case construction mark on the back at all. Again, my tool will ask for this information if it will help narrow things down.
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.
If you have any further information that I could use to date Seiko watches please don't hesitate to get in contact.
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