|Brand:||Seiko, Seiko Instruments Inc.|
|Reserve:||40, 41 hours|
|Winding:||Automatic, Bi-Directional Automatic Winding, Central Rotor Automatic Winding|
|Diameter:||27.40 mm (12 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|
|Distinguishing Technical Characteristics|
Counter-Clockwise Balance Cock
|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.
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.
Seiko 4R35 Operation
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 third position (pulled all the way out). Rotate the crown clockwise to advance the minute and hour hands and counter-clockwise to turn them backward.
Seiko 4R Family Overview
Introduced in 2008, the Seiko Instruments Inc. (SII) 4R family is a mainstream automatic watch movement used in many Seiko models and offered to third parties by Time Module Inc. (TMI). It is an evolution of the Seiko 7S family of movements, produced since 1996, and is related to the higher-end Seiko 6R family.
All movements in the 4R family operate at 21,600 A/h and measure 12 ligne (27.4 mm) in diameter by 5.32 mm in height. Cal. 4R15 and 4R16 have 22 jewels, Cal. 4R35A has 23 jewels, and all other 4R and NH movements have 24 jewels. The NH series movements sold by Time Module Inc. (TMI) are rated as slightly more accurate from the factory, at -20/+40 rather than -35/+45 for the Seiko branded movements, and some differ in the finish, number of jewels, and rated power reserve.
Seiko 4R Movements
There are two branches of the family: The 4R1x movements (4R15, 4R16) came first and have an advanced Spron 510 mainspring but lack hacking and hand-winding. The 4R3x movements (4R35, 4R36, 4R37, 4R38, 4R39, 4R57, 4R71) appeared after 2010 and have a traditional mainspring but add hacking and hand-winding. The 6R family has both improvements.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|