Seiko Automatic Movement: Caliber - 4R35 / 4R36

The Seiko caliber 4R35 is an automatic movement power unit released in 2011. This caliber was considered to be an upgrade from the popular 7S26 movement as it offers the user the desirable hacking and hand-winding functionality. Seiko Caliber 4R35 is exclusive use for their Seiko branded watch only. Unlike the equivalent NH35A caliber, it was often adopted for many micro-brand watches. 

Both Seiko Caliber 4R35 and Seiko Caliber 4R36 share the same specifications, including the dimensions, jewels, accuracy; except Seiko Caliber 4R35 has an extra date calendar display at 3:00 position. 

For more history, before 2010, Seiko commonly uses 4R15 & 4R16 until the launch of Seiko 4R35 & 4R36. 

Furthermore, Seiko Caliber 4R35 comes in two versions, the 23 jewels 4R35A and the  24 jewels 4R35B. As 4R35B 24 jewels are relatively more preferable by the market,  4R35A are rarely found in new models. The Seiko Samurai, the Seiko Mini Turtle, and Seiko Baby Turtles are mainly featured with Caliber 4R35B. 

Caliber 4R35 
Jewels 24
Diameter 27.4mm
Thickness 5.32mm
Frequency 21,600 A/h

Power Reserve ~40 hours
Lift Angle 53 degrees
Regulator System: Etrachron
Hand-Windable: Yes (clockwise)
Functions Hours, minutes, central second hand, date window at 3:00
The accuracy of caliber 4R35 is between +45 / -35 seconds per day. This rating is based on normal daily wear on the wrist in temperatures between 5 ºC and 35 ºC.
Country of Manufacture Japan


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