Grail Watch Reference

A Reference Library for Watches from Grail Watch

Seiko 4R36

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Seiko Cal. 4R36A is a mainstream automatic movement with day and date wheels. It is also offered by Time Module Inc. (TMI) as Cal. NH36A for use by other watch makers. It is closely related to the date-only Cal. 4R35.

Cal. 4R36 was introduced around 2010 and used in the Prospex Automatic watches, Model SRP581 and SRP583 around 2014. It is also used in the Seiko Original line, where the company specifies accuracy to -35/+45 seconds per day and 41 hours power reserve.

Note that Cal. NH36A is rated at -20/+40 seconds accuracy while Cal. 4R36A is rated at -35/+45 seconds. Seiko produces Cal. NH36 in a variety of color and date window variations with black text on a white dial and day and date wheels or reversed, and with the day and date at 3:00 or 6:00. Day wheels are available in English/Spanish, English/Arabic, or English/Chinese.

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. Rotating the crown clockwise in second position corrects the day wheel.

Traditional Mainspring
Hacking/Hand-Winding		Spron 510 Mainspring
Standard4R38A
NH38A
4R71A (skeleton)
NH70A (skeleton)
NH71A (skeleton, gilt)
Date4R35A
4R35B
NH35A		4R15A
4R15B
NH15A
Day and Date4R36A
NH36A		4R16A
4R16B
NH16A
Date, 24 Hour Subdial4R37A
NH37A
24 Hour Subdial4R39A
NH39A
Date by Pointer
Power Reserve		4R57A

Seiko 4R35

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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.

Soprod A10 Modules

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Soprod specializes in modules for other movements, particularly their own A10-2. These were presented in 2010 and released for sale in 2011.

  • SOP 9351/A10: Time zone indicator at 6:00, AM/PM or day/night indicator disc at 10:00, big date at 12:00
  • SOP 9335/A10: Date at 3:00, 24 hour or time zone indicator by pointer at 6:00 (pusher corrector at 4:30), power reserve indicator pointer at 12:00
  • SOP 2021/A10-SO (Dubois Depráz): Automatic chronograph with subdials for seconds, 12 hours, and 30 minutes at 3-6-9 (pushers at 2 and 4), date at 4:30