|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.
The 24 hour hand follows the main hour hand and is not independently adjustable.
The movement can be manually wound with the crown in position 1. Rotate the crown clockwise to wind the mainspring.
The date wheel is advanced with the crown in second position (one notch out). Turn the crown counter-clockwise to advance the date wheel by one day.
The time is set with the crown in second position (pulled all the way out). Rotate the crown clockwise to advance the minute and hour hands and counter-clockwise to turn them backward.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|