Seiko 4S27

	Brand:	Seiko
	Family:	Seiko 4S Family
	Height:	5.38 mm
	Jewels:	28
	Reserve:	40 hours
	Frequency:	28,800 A/h
	Winding:	Automatic, Bi-Directional Automatic Winding
	Diameter:	25.60 mm (11.5 ligne)
	Complications:	24 Hour Hand, Date, Date by Pointer, Day, GMT Hand, Hacking Seconds, Hand Winding, Independently-Adjustable 24 Hour Hand, Modular, Quick Date Correction, Quick Day Correction, Retrograde Day
	Hands:	Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Pointer at 6:00, Retrograde Day Pointer at 2:30

Distinguishing Technical Characteristics
Clockwise Balance Cock Screw Regulator Balance Balance at 4:30 Barrel at 12:00
Production: 2003 – 2007
1910s	1920s	1930s	1940s	1950s	1960s	1970s	1980s	1990s	2000s	2010s	2020s

Cal. 4S27, made from 2003 through 2007, is one of the most complicated automatic movements produced by Seiko. Complications on this modular movement include retrograde day, date by pointer, 24 hour subdial, and independently adjustable hour hand. It was part of the second “wave” of movements in the Seiko 4S family, which itself was derived from the historic Seiko 52 stream of movements. Cal. 4S27 is similar in design to Cal. 4S77, though it lacks the upscale finishing and regulation of that movement. Unlike most 4S movements, Cal. 4S27 has 50 hour power reserve.

Most watches using this movement have the look of a chronograph, with subdials at 6:00 and 9:00 and a power reserve pointer near 3:00. A second crown at 2:00 on the dial adjusts the central 12 hour hand in 1-hour increments, leaving the 24 hour subdial as “home time.” Many examples include a rotating inner bezel with a third crown at 4:00, completing the chronograph look.

• A retrograde pointer at 2:30 shows the day clockwise on a “fan”
• A subdial at 6:00 shows the date using a small pointer
• A subdial at 9:00 shows “home time” using a hand on a 24 hour scale

Cal. 4S27 was used in the Seiko Brightz SAGN Mechanical Retrograde watch series from 2003 through 2007.

• 2003-2007 Seiko Brightz SAGN005
• 2003-2007 Seiko Brightz SAGN007
• 2004-2007 Seiko Brightz SAGN009
• 2004-2007 Seiko Brightz SAGN011
• 2004-2007 Seiko Brightz SAGN013
• 2005-2007 Seiko Brightz SAGN015

Complicated Seiko 4S Movements

After 2000, Seiko had more diverse mechanical movements to choose from. The 4S family was moved upmarket as a base for modules to use in complicated upscale watches. The last 4S movement was retired in 2015.