Grand Seiko Kodo Constant-force Tourbillon Caliber 9ST1

Grand Seiko's first mechanical complication combines a constat-force mechanism and a tourbillon as one unit on a single axis.

In 2020, Grand Seiko introduced the “T0 Constant-force Tourbillon”, a concept movement which incorporated this patented mechanism. To bring the concept to life in a finished watch required the complete dedication of a team comprising designers, engineers and craftsmen and women entrusted with the assembly and finishing of the movement and the case. Each and every one of the 340 components of the caliber was re-examined, and, where necessary, re-designed and re-engineered for production. The result is Caliber 9ST1. Not only is Caliber 9ST1 smaller than its concept movement predecessor but its high accuracy remains stable for longer thanks to the constant-force mechanism. Furthermore, Caliber 9ST1 sets a new standard of accuracy, in which each movement is tested for a full 48 hours in each of six positions and at three tempera- tures. This is twice as long as the Grand Seiko and industry standard. Each movement is assessed over the course of 34 days to verify its accuracy, and when the tests are completed and this new standard has been met or exceeded, the performance characteristics of each movement are defined in the individual certificate provided with every watch.