The 4R35 family was introduced in 2010 as a mainstream automatic watch movement for Seiko watches. It is distinguished by the fact that, unlike earlier mass-market movements like the Seiko 7S26, the 4R3x family hacks and hand winds. It is cost-reduced from the Seiko 4R15/Seiko 6R15 (upon which it is based) and Grand Seiko models, including not using a Spron 510 mainspring.
As of 2018, the 4R35 is used in the SRP family of watches, Seiko's second tier above the 7S26-powered SNK series. Cal. 4R38 and the newer 4R71 is also used in the open heart SSA series. The next series, SBD, uses the 6R15.
Like most Seiko movements, the 4r3x family operate at 21,600 vph. All models feature sweep hour, minute, and second hands. The 4R37 and 4R39 add a 24 hour subdial, while the 4R35 and 4R37 feature a date window and the 4R36 has both day and date in a window. The 4R35 has 23 jewels while the 4R36, 4R37, 4R38, and 4R39 all have 24 jewels. These movements have a power reserve of approximately 41 hours, according to Seiko. Cal. 4R71, introduced in 2018, is designed for use in skeleton dial watches but is otherwise similar to Cal. 4R38.
The 4R35A, which had 23 jewels, was revised shortly after introduction with one extra jewel, becoming the 4R35B.
|4R35A||Hour, minute, seconds||Date||None||23||41 hours|
|4R36||Day and date|
Seiko 7S Family
The following movements were all based on the Seiko 7S26 movement.
|7S||1996||7S25, 7S26, 7S35, 7S36, 7S55||Traditional||No|
|6R1x||2006||6R15, 6R20, 6R21, 6R24||Spron 510||Yes|
|4R1x||2008||4R15, 4R16||Spron 510||No|
|4R3x||2011||4R35, 4R36, 4R37, 4R38, 4R39, 4R71||Traditional||Yes|