Automatic 3-Day Power Reserve GMT

Caliber 9S66

Caliber 9S66 offers all the performance characteristics of Caliber 9S65 — but comes with the addition of the GMT function.

Pulling the crown out by one notch enables the hour hand to be adjusted without stopping the minutes or seconds hand so that the accuracy is not compromised.

The watch is the embodiment of the Grand Seiko pursuit of high accuracy, maintaining exceptional precision in both the essential time display and the GMT function.


Winding mechanism Automatic with manual winding mechanism
Mean daily rate*1 +5 to -3 seconds per day
Normal usage accuracy +10 to -1 seconds per day
Power reserve Approximately 72 hours
Vibrations 28,800 vibrations per hour (8 beats per second)
Number of jewels 35 jewels
Features -Dual time function with 24-hour hand
-Quick correction function of time difference adjusting to a calendar
  1. Mean daily rate is a mean value of daily rates in a condition where the movement before assembly in a case is measured in six positions in a fixed manner under artificially controlled environment for 12 days.

What makes 9S Mechanical special?

The concept of Grand Seiko was born from the desire to build the world's best watch, and the collection continues to push precision in mechanical watches to the limits of timekeeping technology.
As a true manufacture, Grand Seiko combines the latest technology with hand craftsmanship to raise the art of mechanical watchmaking to the highest possible level.