Citizen’s Case Numbers – the Mysterious Case Number Letter

A change today from a watch feature to something that’s always been a bit of a mystery – the letter stamped at the end of Citizen’s case numbers. Although not needed as a part number since the case number alone, e.g. 4-123456 provides that, I have never pinned down just what the additional letter indicates. I wrote to Citizen Japan about it – didn’t get a reply! So I’m left to my own theory 🙂

Most vintage Citizens with the above case number format, typically from the late 1960s and on through the 1970s have ‘TA’, ‘K’ or ‘Y’ stamped alongside the case number:

My theory is that these letters are factory codes – relatively recently I got hold of a scanned catalogue from the early 1970s, and that includes a list of factories:

My best guess is that ‘TA’ is the Tanashi or Tama Seimitsu factory, ‘K’ is the Kawaguchiko factory (dials were made there and dial codes often include ‘KA’ too), and ‘Y’ is …… not so obvious! You can see as well the ‘Star’ Seimitsu Company – older watches have ‘STAR’ marked on them since they initially made cases for Citizen, but later produced smaller parts, particularly screws.

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6 Responses to Citizen’s Case Numbers – the Mysterious Case Number Letter

  1. mike wilensky says:

    Steven, I have tried to write to CASIO/Japan

  2. John says:

    Thanks Stephen, interesting information. I can go and have a look at these mysterious letters on my case backs now.
    Kind regards.

  3. Hafiz cromok says:

    Hello Stephen can u check this citizen watch..

    N-8200-S99156-Y

    CITIZEN WATCH CO
    WATER RESIST
    STAINLESS
    4-581900 HST
    934410
    GN-4-S

    Thanks..
    Hafiz malaysia

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