Seiko (SII) Caliber NH37A
|Caliber Number||NH37A (aka NH37)|
|Vibrations Per Hour
||Bi-directional with one way clutch|
|Diameter||27.40mm (outside) / 29.36mm (casing)|
|Functions||Hours, minutes, central seconds, date calendar, 24 hour indicator|
|Country of Manufacture||Japan/Maylasia|
||AVI-8 Lancaster Bomber (add more in the comments below)|
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
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.