|Brand:||Seiko, Seiko Instruments Inc., Time Module Inc.|
|Winding:||Automatic, Bi-Directional Automatic Winding|
|Diameter:||27.40 mm (12 ligne)|
|Complications:||Date, Day, Quick Date Correction, Quick Day Correction|
|Hands:||Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Window at 3:00, Day Window at 3:00|
|Production: 2008 – Current|
Seiko Cal. 4R16A (commonly called just Cal. 4R16) is an automatic movement with day and date wheels. It was later updated as Cal. 4R16B and is closely related to Cal. 4R15A/4R15B. It is also offered by Time Module Inc. (TMI) as Cal. NH16A with 21 jewels for use by other watch makers. It was the first of a new generation of movements based on the Seiko 7S family and uses a high-spec Spron 510 mainspring as in the related Seiko 6R family for greater than 50 hours running time. Later members of the Seiko 4R family included hacking seconds and hand-winding, but this is not present in the 4R15 or 4R16.
Quick date correction is accomplished with the crown pulled out in second position, rotating counter-clockwise. Rotating the crown clockwise in second position corrects the day wheel.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|