Seiko (SII) Caliber NH37A

The Seiko/TMI/SII caliber NH37 is a hand-windable, hacking variation of the widely popular caliber NH35A – one of the world’s most popular automatic movements and is widely available in many affordable/microbrand watches. In comparison, the NH37A listed here has an additional complication: a 24 hour indicator. This is the only difference between the NH35 and NH37.

Crown Position Functions:

0 (against the case): Clockwise = Manual Winding / Counterclockwise = Nothing
1 (pulled out one click): Clockwise = nothing / Counterclockwise = Date setting
2 (pulled out two clicks): Time setting clockwise and counterclockwise

More Information

Interesting Note: Time Module aka Seiko Instruments labels the NH calibers as part of the “Basic” Mechanical Series. They also have NE calibers that are labeled as “Premium” Mechanical Series.

• For complete specs and drawings, see this pdf
• Parts catalogue for caliber NH37A
• Also see this thread: Seiko NH Caliber Comparison/Differences
• More watch models with the caliber NH35 here
• Difference between SII and TMI

The example above is from an AVI-9 Lancaster Bomber here.