First things first: while this watch is certainly more attainable than the gold SLGH002, it would be hard to describe it as “affordable” with a straight face. The new SLGH003 will sell for $9,700, and is limited to 1,000 pieces. Given the present rarity of the 9SA5 movement, this watch is likely to be highly sought after by collectors and difficult to acquire, but it’s genuinely great news for fans of the brand that Grand Seiko has already figured out a way to get the 9SA5 into a watch for less than $10,000. These types of technological advancements have a way of trickling down to the consumer level, but it usually happens very slowly. To have this movement in a steel watch so soon after its introduction is a great sign.
Before we go much further, let’s quickly review what makes the 9SA5 movement so special. Grand Seiko, for decades, has been a leader in high frequency movements. These calibers beat at a faster rate than a standard movement, and are thus capable of keeping more accurate and stable time. The challenge, as always in watchmaking, is efficiency. With a higher beat rate, you squeeze more energy out of the mainspring, resulting in less power, and shorter power reserve times. Bigger barrels can add hours to the power reserve, but it costs you size. Grand Seiko, with the 9SA5, set out to build a movement that operates at a high beat rate, with Grand Seiko accuracy, for up to 80 hours, without making sacrifices in the size department.
Grand Seiko succeeded here in large part due to the invention of an all new Dual Impulse Escapement, which impulses the balance twice (directly and indirectly) using the same amount of energy that a traditional escapement uses to impulse the balance just once. With the Dual Impulse Escapement, the escape wheel transmits power to the balance directly when it swings in one direction, and indirectly through a traditional pallet fork when swinging in the opposite direction. This makes the 9SA5 significantly more efficient than a traditional high frequency caliber. To make the most out of this saved energy, Grand Seiko was able to fit a second barrel into the caliber without adding significant weight to the movement (thanks in large part to MEMS design principles), allowing for stable timekeeping to +5/-3 seconds per day with 80 hours in the tank.