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You are here: Home / Movements / Seiko 4S12

Seiko 4S12

Last Update: February 5, 2020

Brand:Seiko
Family:
Seiko 4S Family
Height:
Jewels:25
Reserve:40 hours
Frequency:28,800 A/h
Winding:Automatic, Bi-Directional Automatic Winding
Diameter:
  Complications:24 Hour Hand, Date, GMT Hand, 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
Clockwise Balance Cock
Screw Regulator
Balance
Balance at 4:30
Barrel at 12:00
Production: 1997 – 1998
1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s 2020s

Cal. 4S12 is an automatic movement with date and 24 hour hand developed by Seiko in the early 1990s. It was based on the Seiko 52 stream of movements, which had been retired in 1976, and was responsible for Seiko’s resurgence as a maker of high-end watches. Cal. 4S12 is very similar to Cal. 4S15, which lacks the 24 hour hand.

The 24 hour hand is located centrally on the dial, coaxial with the ordinary timekeeping hands. It is not adjustable separately from the 12 hour hand. This leads some to consider it not to be a “true GMT”, though this is the same function as the famous Rolex GMT-Master.

Cal. 4S12 was used in the SUS GMT military watch, which included an internal rotating bezel to enable the user to “set” the GMT hand for a second time zone.

  • Seiko SUS SCFF005
  • Seiko SUS SCFF007
  • Seiko SUS SCFF009
This catalog image shows the three Seiko SUS GMT SCFF models

Early Seiko 4S Movements

From the 1992 introduction of the Seiko 4S family through the early 2000s, Seiko used the 4S line as a high-end movement for diverse watches, including the SUS military, Alpinist, and Titanium diver. Most of these models were retired shortly after introduction, and the series of simple 4S movements was phased out by 2003.

ProductionWatchWindingJewelsNotes
4S121997-1998SCFFAutomatic25Date
Fixed 24 hour hand
4S151995-2001
2006
LHAM
SCFF
SCVF
SCVN
Automatic25Date
4S241990sLJAL
SCVG
Manual21
4S251993-1998SCVH
SCVJ
Automatic25Date
4S281994-2000LJAK
SCVG
SCVM
Manual24Small seconds at 6:00
4S351992-2000SCVKAutomatic25Date
4S711995-2003GCBBAutomatic25
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
External Link

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