Seiko Caliber Nh37

Seiko (SII) Caliber NH37A

Seiko SII Caliber NH35

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.

Seiko Caliber Nh37

Seiko Caliber Nh37a

Seiko Nh37a Gears

Seiko Nh37a Anti Shock

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

Is the Seiko (SII) Caliber NH37A any good? Share your opinions, experiences and watches below... Keep comments respectful and follow our community guidelines.

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Seiko Caliber NHxx Variation Differences Watch Movement |

[…] NH37 (Seiko 4R37) […]

Frederik de Haan
Frederik de Haan

These NH XX movements are true marvels in their own right !