Seiko Cal. 4R39A (commonly called just Cal. 4R39) is a mainstream automatic movement with open heart balance at 9:00 and 24 hour subdial at 10:30. It is also offered by Time Module Inc. (TMI) as Cal. NH39A for use by other watch makers. It is closely related to the date-only Cal. 4R35 and the Cal. 4R37 and 4R38.
Cal. 4R39 was introduced around 2011 and used in the Premier Automatic watch with 24-hour Indicator, model SSA021, SSA023, SSA024, SSA213, SSA215, and SSA216. The first series was produced from 2011 through 2013, with the second series introduced in 2014 and produced through 2018.
Hand winding is accomplished with the crown in first position, rotating clockwise. The 24 hour hand follows the main hour hand.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|