| Manufacturer | Seiko |
| Caliber Number | NH37A (aka NH37) |
| Base Caliber | NH35A |
| Movement Type | Automatic |
| Jewels | 24 |
| Vibrations Per Hour |
21,600 bph |
| Shock System | Diashock |
| Power Reserve |
41 hours |
| Winding Direction |
Bi-directional with one way clutch |
| Hacking? | Yes |
| Hand-Windable? | Yes |
| Diameter | 27.40mm (outside) / 29.36mm (casing) |
| Height | 5.32mm |
| Functions | Hours, minutes, central seconds, date calendar, 24 hour indicator |
| Country of Manufacture | Japan/Malaysia |
| Known Brands |
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
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.
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