|Brand:||Seiko, Seiko Instruments Inc.|
|Reserve:||40, 41 hours|
|Winding:||Automatic, Bi-Directional Automatic Winding|
|Diameter:||27.4 mm ( ligne)|
|Complications:||Date, Hacking Seconds, Hand Winding, Quick Date Correction|
|Hands:||Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Window at 3:00|
|Production: 2010 – Current|
The Seiko Cal. 4R35 is an automatic watch movement with date. It is produced by Seiko Instruments Inc. (SII) and is also known as Cal. NH35 when sold by Time Module Inc. (TMI) to third-party watch makers. The initial Cal. 4R35/4R35A, introduced in 2010, had 23 jewels while the similar Cal. 4R36/4R36A (with day wheel) had 24. Seiko later used the extra jewel in the count for the Cal. 4R35B. This is the current movement offered.
The Cal. 4R3x family of movements is an evolution of the classic Seiko 7S family, updated with hacking seconds and hand winding. It is related to the Seiko 4R1x and Seiko 6R1x families, which feature an advanced Spron 510 mainspring.
Cal. 4R35 was introduced around 2010 and used in the Premier Automatic watches, model SRPA17 starting in 2016. It is also used in the Seiko Original line, where the company specifies accuracy to -35/+45 seconds per day, 41 hours power reserve, and 23 jewels.
Note that Cal. NH35 is rated to -30/+45 seconds accuracy while Cal. 4R36B is rated to -35/+45 seconds. Seiko produces Cal. NH35 in a variety of color and date window variations with black text on a white dial and date wheel or reversed and with the 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.