The never-ending quest to achieve a longer power reserve

Put simply, the more powerful the mainspring, the longer the power reserve. This fundamental rule sets a challenge for Grand Seiko that its engineers have striven continuously to meet.

The first Grand Seiko 9S caliber, created in 1998, had a power reserve of around 50 hours, a duration that was already longer than that of all its predecessors. Thanks to a unique SPRON alloy and in-house engineering skills that allowed improvements to the length, thickness and width of the mainspring, the current 8-beat movement, Caliber 9S65, offers a reserve of about 72 hours. Advances were also made with the 2009 hi-beat Caliber 9S85. Despite the fact that this 10-beat movement required greater torque, the creation of another new SPRON alloy gave this hi-beat caliber a power reserve of approximately 55 hours. The 2020 hi-beat Caliber 9SA5 again raised the bar with a reserve of approximately 80 hours thanks to its Dual Impulse Escapement and its Twin-Barrel system.

In every respect, the Caliber 9S series of mechanical movements has evolved over the past 25 years to offer ever-increasing levels of performance, as the enhancement of the power reserve bears powerful witness.