The Grand Seiko U.F.A. Caliber 9RB2 is the most accomplished Spring Drive movement the company has yet produced, since the technology first debuted over two decades ago. It represents a ground-up refinement of both regulating and transmission system, created to achieve a level of precision that no main spring-driven watch has ever claimed before. Its rated performance of±20secondsperyearisasixfoldimprovementover the ±10 seconds per month of the 9RA2, and while that headline figure might seem like the result of a technological breakthrough, it is instead the outcome of subtle but decisive changes across both the quartz and mechanical domains of the movement.

Grand Seiko Spring Drive U.F.A. SLGB0003

At the heart of this evolution is the quartz oscillator. Like the movements before, the 9RB2 employs an oscillator that has been aged for three months to stabilize its frequency and then sealed, together with the thermistor, IC (integrated circuit) and wiring, in a vacuum package to shield the system from humidity, static and light. What has changed is how that oscillator is processed. Quartz, being crystalline, carries within it residual stress from the way it is cut, and over time that stress can express itself as minuscule shifts in oscillation frequency. In the 9RB2, new methods of relieving this stress have been introduced, reducing the tendency of the crystal to “relax” back to its original state. It is a refinement that cannot be seen by the owner, but one that yields a steadier rate over the course of years.

Calibre 9RB2

The “brain” that governs the crystal has also been rethought. The integrated circuit is newly designed, still operating at ultra low power but with its logic refined to suppress even the smallest variations in frequency. Every oscillator drifts slightly depending on temperature, and in the Spring Drive, that drift is checked 540 times a day, with each reading used to apply thermo-compensation and keep the rate steady across the range of everyday wear. In the 9RB2, these corrections are applied with greater precision, ensuring that deviations are contained before they can accumulate. Additionally, for the first time, the Caliber 9RB2 incorporates a regulation switch, enabling fine adjustment during servicing to correct for long-term frequency drift.

On the mechanical side, the changes are just as significant, though they are aimed at stability rather than duration. Where the 9RA2 relied on two serially coupled barrels for a five-day power reserve, the 9RB2 pares this back to a single barrel with a 72-hour power reserve. However, mainspring torque has been increased and the profile of the gear teeth redesigned to improve transmission efficiency. Energy is now delivered with less loss across the train, and the glide wheel, which is responsible for converting that energy into Spring Drive’s seamless sweep, receives a steadier flow of torque.

The blue textured dial

The movement remains 30mm in diameter, the same as 9R65, but its magnetic shielding is divided into four discrete sections, arranged within the available clearance spaces on either side of the movement, allowing it to be cased at 37mm for the first time.

The 9RB2, in essence, extends the logic of Spring Drive to its furthest expression where every component works to suppress variation. The achievement is not simply in hitting ±20 seconds per year but in creating a system that can realistically sustain that performance in daily use and maintain it through the years with service regulation. It is the clearest statement that at Grand Seiko, even a technology that has long reached maturity can still find new ways to evolve in pursuit of timekeeping at its highest possible level.

Grand Seiko Spring Drive U.F.A. SLGB001

Tech Specs: Grand Seiko Spring Drive U.F.A. SLGB001 & SLGB003

Movement Self-winding Spring Drive Caliber 9RB2; 72-hour power reserve
Functions Hours, minutes, seconds and date
Case 37mm × 11.4mm; High-Intensity Titanium (SLGB003) or platinum (SLGB001); water resistant to 100m
Dial Silver-tinged blue textured (SLGB003), or deeper blue textured (SLGB001)
Strap High-Intensity Titanium bracelet with three-step micro-adjustment folding clasp (SLGB003); crocodile leather with triple folding clasp in platinum (SLGB001)