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.
Related photographs
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No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- Manufacturer technical documentation for the 9S calibre family
Where sources disagree, the disagreement is stated rather than resolved silently.