Seiko caliber 6309

Seiko Caliber 6309

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Seiko caliber 6309

Brand Seiko
Caliber Number 6309, 6309A
Movement Type Automatic
Jewels 17
Vibrations Per Hour
21,600 bph
Power Reserve 47 hours
Diameter 12”’ (27mm)
Thickness 5.3mm
Shock System Diashock
Rotor Ball bearing
Mainspring 401615
Balance Staff 311601
Hands 1.5 x .90 x .20
Hacking? No
Manual Winding? No
Crown Location 3:00
Functions Hours, minutes, central seconds, quickset bi-lingual day, quickset date
Country of Manufacture Japan
Known Models 6309 (add more in the comments below)

The Seiko caliber 6309 is a vintage automatic workhorse movement that was found in many Scuba Diver models, seiko 5, and dress watches in the 1980’s. There are different variations of this movement, including Seiko caliber 6308A (17J), 6319A (21J), 6347A (moonphase, 23J), 6349A (23J).

In old Seiko documentation, they refer to the 6309 as a Highly Reliable Movement:

The highly stabilized accuracy and high reliability established for the 61XX series has been incorporated into the movement.

Also mentioning easy servicing:

Disassembling and reassembling procedures and serviceability have been improved largely by:

  • Employment of a new balance hairspring holding device (aka no stud for the hairspring since it clamps directly in the terminal)
  • Decrease in number of parts from the simplification of the movement structure.
  • Decrease in number of new parts resulting from interchangeability of some parts with Cal. 61XX series.

In an interesting thread on the Military Watch Resource forum comparing the Seiko caliber 6309 to the ETA caliber 2824, shortwave said:

I have a 25 year old 6309 7290. It hasn’t been cleaned in at least 10 years. It advances 1 to 2 seconds in 12 days. I’ve never seen such accuracy in any manual watch. The ETA in my Marathon, gains seconds a day.


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He tenido seikos con este calibre 6309 y son fabulosos van mas exactos y precisos que otros relojes que montan maquinas eta, sellita o unitas., son unos autenticos caballos de batalla sencillos, fiables, precisos y robustos.

Jonathan Shaw

I have just bought one of these movements in a bit of a frankenwatch, its got a really cool retro orange with green circle face, except I’m pretty sure its not the original case due to the way the case’s internal outer edge cuts off the numbers 2/4/8/9 and 10, I might even have a go at removing this part of the case to get the full face on show, it would make a desirable vintage 5 if I could sort that out, oh and sinceI got the watch it has been running fast, I’m trying to use the regulator… Read more »


I own this watch since August 1987. First time was cleaned after ten years of service. After few adjustments, accuracy reached a couple of seconds per week, amazing for an automatic, mid-to-low end, general purpose watch.


Can anyone tell me if someone has the correct Lift angle for this caliber or if there are any calibers similar to this one.


I have a Seiko 6309-729A 150M diver. I had got it in 1988 as a gift. As a young boy I used it a lot for many years. However, it was neglected and kept in a drawer for the last 20 years as I used various other watches. As part of house cleaning, just found it. Just washed it and cleaned it myself. And it is working fine. What a sturdy movement. It has been working fine. A question – should I get it serviced? Everything seems fine. I just don’t want some service shop to messup. Thanks for answer… Read more »


I am 32 years old now and it is still on my father’s arm… I think i had opened my eyes to world with that machine… And now unfortunately, it needs a service… It is stopped in a sudden…


Reliability? 6309-8920 blue dial with dented crown and much scratches all over the watch. 35 years old. Stopped working for about than 10 years. Inherited it from my dad. No servicing was done since manufactured. Shake it hard for a couple of minutes. It’s running like usual again. Opened up the back case, no corrosion and very minor dirt deposit on the gears. A true power horse indeed.


[…] 6309 designation is for a Seiko automatic movement with 17 jewels and 47 hours of power reserve. It beats at 21,600 […]

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