|Brand:||Seiko, Seiko Instruments Inc.|
|Winding:||Automatic, Bi-Directional Automatic Winding|
|Diameter:||27.40 mm (12 ligne)|
|Complications:||24 Hour Hand, Date, Hacking Seconds, Hand Winding, Quick Date Correction|
|Hands:||24 Hour Hand at 10:30, Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Window at 3:00|
|Production: – Current|
Seiko Cal. 4R37A (commonly called just Cal. 4R37) is a mainstream automatic movement with date window at 3:00 and 24 hour subdial at 10:30. It is also offered by Time Module Inc. (TMI) as Cal. NH37A for use by other watch makers. It is closely related to the date-only Cal. 4R35 and the Cal. 4R38 and 4R39.
Cal. NH37 is available with a white dial and black lettering or the reverse, and with date at 3:00 or 6:00.
Hand winding is accomplished with the crown in first position, rotating clockwise. Quick date correction is accomplished with the crown pulled out in second position, rotating counter-clockwise. The 24 hour hand follows the main hour hand.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|