Cal. 9S66 is an automatic movement with date and GMT hand from Grand Seiko. It was introduced in 2010 alongside the similar Cal. 9S65, which lacks the GMT hand. The central 24 hour hand is independently adjustable using the crown in first position, and the movement continues to run while adjusting it.
Cal. 9S66 is used in the Grand Seiko SBGM series of watches.
Seiko 9S6x Family Overview
9S is the family of high-end mechanical watch movements used in the Grand Seiko and Credor watch lines. The current “3 days” 9S6x family debuted in 2006 with Cal. 9S67, and has replaced the Seiko 9S5x series over the following decade. The movement boasts 72 hours of power reserve thanks to a stronger Spron 510 or 610 mainspring and escape wheel and pallet form finished with MEMS technology.
Seiko boasts that these movements can deliver -3/+5 seconds per day accuracy in controlled static tests. On the wrist, the company claims -1/+10 second accuracy per day, and Seiko adjusts them in 6 positions. Adjustment is performed using a screw with index moving a mobile regulator for the flat hairspring.
The 9S family movements are constructed by hand at Seiko’s Shizukuishi Watch Studio in Morioka, Iwate Prefecture, Japan.
All watches in the 9S6x series feature hand winding, hacking seconds, and operation at 28,800 A/h. Most feature automatic winding with a central rotor mounted on five ball bearings. These use a conventional reverser wheel rather than the Seiko Magic Lever system found on the previous Cal. 9S5x series.
Seiko 9S6x Family
| Production | Models | Winding | Jewels | Date | Notes | |
|---|---|---|---|---|---|---|
| Cal. 9S61 | 2015-present | SBGR | Automatic | 33 | No | |
| Cal. 9S63 | 2019-present | SBGK | Manual | 33 | No | Power reserve at 3:00 Small seconds at 9:00 |
| Cal. 9S64 | 2011-present | SBGW | Manual | 24 | No | |
| Cal. 9S65 | 2010-present | SBGR | Automatic | 35 | Yes | |
| Cal. 9S66 | 2010-present | SBGM | Automatic | 35 | Yes | Central GMT hand |
| Cal. 9S67 | 2006-2010 | SBGL | Automatic | 41 | Yes | Power reserve at 3:00 |
| Cal. 9S68 | 2017-present | SBGR | Automatic | 35 | Yes | Larger size |
See Also: Seiko 9S6x Family