Unveiled in 2020 by the Shinshu Watch Studio, Caliber 9RA5 is Grand Seiko’s next-generation Spring Drive movement. It's slimmer, more accurate, and has a longer power reserve thanks to a number of important updates and innovations.
9RA5 was developed by movement designer Eiichi Hiraya. Hiraya and his team developed a new IC package featuring thermo-compensation, improving accuracy to +-10 seconds a month maximum deviation. The movement is also slimmer; an offset Magic Lever did away with about .8mm in movement thickness. To ensure robustness, the gear train was redone to fit along the central horizontal axis of the movement and locked in under a one-piece center bridge. Hiraya implemented the use of dual-size barrels on the same plane in the movement to achieve a longer power reserve. Because these two barrels are different sizes, they can fit inside the allotted area without sacrificing performance, all the while maintaining the desired thinness of the caliber and a whopping 120-hour, or five-day, power reserve.
The first watch featuring this caliber is Reference SLGA001, a professional diver rated to 600m and designed for maximum legibility. The case of SLGA001 is high-intensity titanium, which is 40% lighter than steel and more impervious to scratches. The power reserve is at the 10 o'clock position and the indicator is divided into five parts to show exactly how many days are left in the power reserve. The case, crystal, and bezel are all designed for easy and safe disassembly for the maintenance that a professional diver demands. The dial color is Grand Seiko blue, a special color that symbolizes the brand.
SLGA001 is a limited edition of 700 pieces.