Movement record · Japan (Shizukuishi, Iwate)
Seiko calibre 9S55
VerifiedThe mechanical calibre with which Seiko resumed high-grade mechanical production at the Shizukuishi studio, assembled and adjusted by hand to an in-house accuracy specification stricter than the standard chronometer test.
Technical specifications
- Diameter
- 28.4 mm
- Height
- 5.15 mm
- Jewels
- 26 jewels
- Frequency
- 28,800 vibrations per hour
- Power reserve
- Approximately 50 hours
- Winding
- Automatic with manual winding and hacking seconds
- Setting
- Crown setting with date quickset
- Escapement
- Swiss lever with Seiko's own Spron hairspring material
- Balance
- Jewelled, regulated to Grand Seiko's own accuracy standard
- Complications
- Date, Stop seconds
Identification features
- Calibre number engraved on the movement
- Grand Seiko accuracy specification stated on the accompanying documents
Known variants
- 9S55 and related 9S5x family members
Servicing notes
Factory service is strongly preferred; Seiko's own hairspring and mainspring alloys are not generally available to the trade.
General guidance only. Antique movements should be serviced by a qualified watchmaker.
Historical significance
Marks Seiko's return to high-grade mechanical watchmaking after the quartz era and the basis of the modern Grand Seiko mechanical line.
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Manufacturer technical documentation for the 9S calibre family
Where sources disagree, the disagreement is stated rather than resolved silently.