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WatchtheDetails

Watch serial number lookup

A serial dates a Seiko, Bulova or Timex — usually to a few candidate years, not one. A Casio serial dates nothing; its module number tells you what is inside.

Sources checked · How we source numbers
Seiko case back: calibre 7S26, serial 8N0123STAINLESS STEEL · WATER RESISTANT · STAINLESS STEEL · WATER RESISTANT · STAINLESS STEEL · WATER RESISTANT · 7S261-····calibre – case code82N301234serial: year · month · production number
Our drawing, not a photo: 1 calibre, 2 year digit, 3 month, 4 production number.

What each brand’s serial can tell you

Where to look, what the code gives, and one example worked through each brand’s rules.

  • Where to look

    The 6-character serial on the case back, under the ####-#### calibre and case code.

    What it tells you

    The last digit of the year and the month. Not the decade: that comes from the calibre’s production years.[1][2][3][4][5][6]

    Example

    8N0123 alone: November 1968, 1978, 1988, 1998, 2008 or 2018. With a 7S26: November 1998, 2008 or 2018.

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  • Where to look

    A letter and a digit on the case back, often on the movement too (from 1950); a symbol on the movement before.

    What it tells you

    The year: the letter is the decade, the digit the year. A8 and A9 are ambiguous.[7][8][9][10][11]

    Example

    N5 is 1975.

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  • Where to look

    The number at the bottom of a mechanical dial (1963–1993), or two characters on the case back (1985 on).

    What it tells you

    The year from the dial code; year and month from the case back, with two dates about 29 years apart.[12][13][14]

    Example

    Dial 2495210592: 1992. Case back 05: May 1985 or 2014.

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  • Where to look

    The module number in a small box on the case back, and the model number.

    What it tells you

    No date. The module names the electronics and the manual; the model names the watch.[15][16][17]

    Example

    Module 5611: 91 models in Casio’s index.

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Why the answer is often several years

Watch date codes were made for the factory, not for owners decades later. They are short, so they repeat: a Seiko year digit every ten years, a Timex case-back code after about 29. A lookup that prints a single year without other evidence is guessing.

Our decoders list every year a code can mean and remove a year only when something rules it out — the production years of the movement, a revision letter, a model that was not yet made — and they show each removed year with its reason and its source.

A blank steel caseback under a jeweller's loupe in raking light, showing fine scratches and no engraving.

Questions

Can a serial number tell me how old my watch is?

For Seiko, Bulova and Timex, usually to within a few candidate years. A Seiko serial gives the year's last digit and the month (8N0123 is November of a year ending in 8); the calibre narrows the decade. A Bulova code gives the year outright (N5 is 1975). A Casio serial gives no date at all.

Why does a serial number lookup give several years?

Because the codes are short and repeat. Seiko writes one digit for the year, so it comes back every ten years; Timex reused its case-back codes about 29 years later. Only other evidence — the calibre, the model’s years, the style of the watch — can rule a year out, and we only rule one out when there is such evidence.

Are these serial rules published by the watch brands?

No. Seiko, Timex and Casio publish none that we could find, and Bulova’s own chart could not be read when we checked. The rules come from collector sites, checked against each other; every rule on these pages names its source, and where sources disagree both readings are shown.

Sources

Documents checked · Report a wrong number

  1. 1Plus9Time — Deciphering Seiko Case Back Information · html · read
  2. 2Serial-Number-Decoder.co.uk — Seiko Serial Number Decoder. Find the date of a Seiko by serial numnber · html · read
  3. 3Serial-Number-Decoder.co.uk — Date a Seiko by serial number. How to decode a Seiko serial number to find production date · html · read
  4. 4WatchScanning — Seiko Serial Number Lookup (2026): Decode Your Watch's Production Date · html · read
  5. 5Grail Watch — Seiko 7S26 (Grail Watch Reference) · html · read
  6. 6EmmyWatch — Date Your Seiko Watch By Serial Number - EmmyWatch · html · read
  7. 7OttUhr — How Old Is My Bulova Watch? The Complete Bulova Date Code Guide · html · read
  8. 8WatchScanning — Bulova Date Code Decoder: Serial Number Lookup · html · read
  9. 9The Watch Guy — The Watch Guy: Bulova Serial Number Table & Manufacture Dates · html · read
  10. 10PocketWatchRepair.com (Renaissance Watch Repair) — Bulova Watch Company: History, Date-Codes and Date-Symbols · html · read
  11. 11Brittons Watches — Bulova watch list of serial numbers to date your watch · html · read
  12. 12Wikibooks (Budget Watch Collecting) — Budget Watch Collecting/Timex date codes · html · read
  13. 13Vintage Timex Watches — Vintage Timex Watches: Collector's Guide to Models & Dating · html · read
  14. 14Vintage Timex Watches — Vintage Timex Case-Back Stamped Codes · html · read
  15. 15Majestix Collection — How to Check Casio Watch Serial Number Correctly · html · read
  16. 16Watch Identifier — Casio Watch Identifier: Module and Model Numbers Explained · html · read
  17. 17Serial-Number-Decoder.co.uk — Casio serial number decoder. Date a Casio by serial number, batch code or module · html · read