(Image credit: SteveG)
The 6S37 is an Automatic chronograph movement from Seiko, used in their Flightmaster and also OEM's as the SII TC78. As the TC78, it's the base movement for the Tag Heuer 1887, an unknown Junghans and probably others.
Here's a blown-up pic from Tag:
(Image credit: Tag Heuer via Watch Happening)
- 28mm by 7.27mm
- Rhodium plated
- Tilting pinion, column wheel coordination
- Automatic, bidirectional winding, Seiko magic lever system
- Handwinding and hacking
- 40 jewels
- 28,800 vph
- 50 hour power reserve
- Over 300 parts
- Accuracy: +10/-15 seconds/day
- SteveG's pictorial review
- Randall Benson's movement review
- Watch Happening on the 1887
- Calibre 11 is where I learned that Tag was OEMing their new chronograph from Seiko. Worth a read - Tag reps posted nice comments explaining the changes they made to the movement.
- Link on WatchUSeek discussing the Tag.
- TimeZone post on the history of the Flightmaster and the 6S37
- Seiya sells Flightmasters here