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You are here: Home / Movements / Seiko 4R38

Seiko 4R38

Last Update: July 7, 2019

Brand:Seiko, Seiko Instruments Inc.
Family:
Seiko 4R Family
Height:5.32 mm
Jewels:24
Reserve:40, 41 hours
Frequency:21,600 A/h
Winding:Automatic, Bi-Directional Automatic Winding, Central Rotor Automatic Winding
Diameter:27.40 mm (12 ligne)
  Complications:Hacking Seconds, Hand Winding
Hands:Central Hour Hand, Central Minute Hand, Central Seconds Hand, Open Heart at 9:00
Distinguishing Technical Characteristics
Central-Rotor Automatic
Counter-Clockwise Balance Cock
Etachron Regulator
Balance
Balance at 3:00
Central Rotor
Production: 2012 – Current
1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 2020s

Seiko Cal. 4R38A (commonly called just Cal. 4R38) is a mainstream automatic movement with open heart balance at 9:00. It is also offered by Time Module Inc. (TMI) as Cal. NH38A for use by other watch makers. It is closely related to the date-only Cal. 4R35 and the Cal. 4R37 and 4R39, both of which have a 24 hour subdial at 10:00.

Cal. 4R38A is also used in the Seiko Original line, where the company specifies accuracy to -35/+45 seconds per day and 41 hours power reserve.

Seiko 4R38 Watches

Seiko SSA409 with Cal. 4R38A

Seiko uses Cal. 4R38 in a variety of watches, most of which feature an “open heart” to view the balance at 9:00. Most watches using this movement use code SSA in the United States and SARY or SSVM in Japan.

  • Seiko Presage SSA257, SSA258, SSA262, SSA358, SSA359, SSA405, SSA407, SSA409, SSA859
  • Seiko Ladies Automatic, SSA781, SSA783, SSA785, SSA848, SSA850, SSA852, SSA854, SSA860, SSA862, SSA863
  • Seiko Sportura Automatic, SSA884, SSA885
  • Seiko 5 Sport, SSA327, SSA331

Seiko 4R38 Operation

The movement can be manually wound with the crown in position 1. Rotate the crown clockwise to wind the mainspring.

The time is set with the crown in second 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.

There are only a few complicated members of the family, with a 24 hour subdial (4R37 and 4R39), or date by pointer subdial and power reserve indicator (4R57).

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
Images are taken from official publications and are used here for commentary and educational purposes. Copyright is held by the original owner as noted.
External Link
Manufacturer Link

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