Manufacturer | Seiko (SII, TMI) |
Caliber Number | NH38, NH38A |
Movement Type | Automatic, self-winding mechanical |
Diameter |
27.40mm |
Casing Diameter |
29.36mm |
Height |
5.32mm |
Jewels | 24 |
Vibrations Per Hour |
21,600 bph |
Lift Angle |
53 degrees |
Accuracy Rating |
-20~+40 sec/day average |
Power Reserve |
41 hours |
Rotor Winding Direction |
Bi-directional (Seiko Magic Lever) |
Manual-Winding? |
Yes |
Anti-Shock System | Diashock |
Hand Count |
3 |
Functions | Central hours; central minutes; central sweeping seconds |
Notable Features |
True no-date, open balance wheel |
Hacking Seconds? | Yes |
Country of Manufacture | Japan/Malaysia |
Known Brands |
Various Invicta, Gruppo Gamma Venturo Feild II (Add your watch in the comments below…) |
The Seiko caliber NH38A is very similar to the popular caliber NH35A.The NH38 series is often found with an open balance wheel at 9:00 on the dial. The NH38A is a 3-hander “no-date” movement. It is a true no-nate without a phantom date crown position.
Some of the topics covered in this caliber listing:
What is the difference between the NH38A and NH35A?
The NH38A is the no-date version of the NH35A. Unlike the NH35A, the NH38A is a basic three hand watch and does not have a day or date complication. Another difference is that the NH38A is partially skeltonized with an open balance wheel.
Accuracy Rating:
Time Module (TMI) claims an accuracy rating of -20~+40 seconds per day.
Japan or Malaysia or…?
The complete Japanese-made caliber number is NH38A3J. For the Malaysia variant, the official number is NH38A3M. Regardless of where the movement was made, these longer numbers are mostly for ordering purposes and not found anywhere on the movement itself. Most are not marked with a country of origin… so, technically, who knows!
Other examples of this movement:
The large photo below is of a Seiko NH38A movement in an Invicta 22744 watch.
Image above submitted by Nathaniel B.
Additional Resources:
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