Seiko Caliber 6309

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.

Note: This caliber is sometimes mistaken as being 6809 (6809A) by folks who can’t see the 3 clearly.

In Seiko’s own words:

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.

Variations:

There are different variations of this movement, including Seiko caliber 6308A (17J), 6319A (21J), 6347A (moonphase, 23J), 6349A (23J).

Community Commentary:

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.

Video of Servicing:

Additional Resources:

• View more Seiko calibers here
• Shop Seiko watches here