Seiko Cronos 50M calibre : 54-00-2

P1060229

Seiko’s first swim-friendly watches were Cronos Seahorse in 1960. In 1962 the Cronos replaced seahorse with water 50 proof. This watch is in good condition, but can do with a service. 

P1060230

I dig the Seiko balance bridge construction! Movement looks very good.

P1060231

Broken setting lever spring… Good news is I have found some in Japan.

P1060233

I take the setting/winding mechanism apart.

P1060234

Seiko did not save on the amount of jewels in this movement…

P1060235

The only marking I find to indicate calibre name is T40?

P1060236

Movement almost apart.

P1060237

The old mainspring looks pretty good.

P1070303

I have cleaned the movement and here I see that the balance moves freely after fitting the shock jewels.

P1070305

Mainspring has been cleaned, oiled and put back into the barrel.

P1070306

The barrel and centre wheel goes back in place.

P1070307

Here you can see the gear train layout before fitting the bridge.

P1070308

I like the colouring of the lettering.

P1070309

The new setting lever spring.

P1070313

Setting/winding mechanism back in place with the new setting lever spring.

P1070310

The movement is almost back together.

P1070311

I fit the balance and the movement is running.

P1070312

The result is very good!

P1070314

Dial and hands go back onto the movement.

P1060238

I take the case apart and clean it.

P1070301

I use a NOS crystal.

P1070316

Movement goes into the case, looking great!

P1070317

Awesome watch.

P1070323

This I would consider a genuine sports watch:)

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6 Responses to Seiko Cronos 50M calibre : 54-00-2

  1. Andrew Cookson says:

    Great post Mitka – i had to work on an FHF 72 a couple of weeks ago and was struck reading today’s entry how structurally similar the movements are: http://17jewels.info/movements-en/movements-f-en/movements-f-fhf-en/770-fhf-72.html

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  2. matabog says:

    Nice Balance bridge! Too bad you cannot set the beat error the easy way, though!

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  3. huangcjz says:

    Dear Mitka, I hope you’re well.

    For your information, the calibre number of the non-date Cronos movement is 54-00-2 (or 5400 or 54A in Seiko’s newer movement numbering system), and the calibre number for the early (pre-760/850/760x) Seiko Champion movement that you also serviced is 54-20-1 (or I would guess 5420 or 5420A in Seiko’s newer movement numbering system), as seen here: https://www.tapatalk.com/groups/seikoholicssupportforum/an-old-post-about-caliber-numbers-t381.html
    People often call the early (pre-760/850/760x) Seiko Champion movements (and the first-generation, non-hacking King Seiko movement 54-40-1) “un-numbered”, since these numbers are not widely known.

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