Watchmaking records, ranging from ultra-thin watches with the thickness of two credit cards to the highest chronograph operating frequency, are being broken left, right and centre. These days, whenever a new timekeeping accuracy record is broken, you can count on Grand Seiko being in the mix. This year at Watches & Wonders, the Japanese watchmaker not only broke but also smashed the record with the new Spring Drive Calibre 9RB2, featuring the U.F.A. designation.
The U.F.A. (Ultra Fine Accuracy) designation can be considered as a descendant of Grand Seiko’s 1969 V.F.A. (Very Fine Adjusted) accomplishments — achieving an astonishing ±1 minute monthly deviation. Even though the V.F.A. did not reach its fullest potential, it paved the way for another groundbreaking innovation of its kind, the Spring Drive. In brief, the Spring Drive combines quartz and mechanical features into an electromechanical design. Essentially, all the components of a mechanical calibre, except its escapement, are present in a Spring Drive watch. The glide wheel takes that spot, driven by mechanical power from the mainspring. It makes eight full revolutions per second, which generates a small electric current in the process. From there, the electrical power activates a quartz oscillator and integrated circuit (IC). The quartz oscillator vibrates exactly at 32,768 Hz, which the IC uses as a reference signal and continuously monitors against the glide wheel’s rate. An intermittent braking force is applied via electromagnetic power to ensure the glide wheel rotates precisely eight times per second. This trio of components form what is known as the Tri-synchro Regulator.
The Spring Drive officially debuted in 2004 as part of the Spring Drive Calibre 9R65, featuring a monthly deviation of ±15 seconds that set a new standard among movements powered by a mainspring. Since then, Grand Seiko has unveiled a series of Spring Drive movements, including the Spring Drive Calibre 9RA2 and this year’s record-breaking posterchild, the Spring Drive Calibre 9RB2. By comparison, the former has an accuracy rate of ±10 seconds per month while the latter has a mind-boggling accuracy rate of ±20 seconds per year, making it the most accurate watch powered by a mainspring.
Much of the improvement to the Spring Drive general blueprint was incremental rather than revolutionary, allowing for this milestone in accuracy to be achieved. Its quartz oscillator was aged for three months to accompany a newly designed IC. Both the oscillator and sensor are vacuum sealed to minimise temperature fluctuations and protect against humidity, static, and light, ensuring a stable environment for the components. What is new, however, and a first for any Spring Drive movement, is a regulation switch to correct deviations during after-sales service.
The Spring Drive Calibre 9RB2 is housed in the new Grand Seiko Evolution 9 SLGB001 (limited edition of 80 pieces) and SLGB003. The former is housed in a platinum case and paired with a crocodile strap, while the latter is in Grand Seiko’s High-Intensity Titanium case and bracelet. Both are rendered with Grand Seiko’s signature distortion-free, mirror-finish Zaratsu polish that alternates with soft brush finishing. As with Grand Seiko’s efforts in recent years, it manages to converge artistry and technicality into a single package. Here, frost-covered trees of the Kirigamine Highlands are captured on the intricately textured dials. A deeper blue hue shimmers from the SLGB003 dial, while the silver-tinged dial of SLGB001 exudes a slight hint of blue.
The duo moves into mid-sized watch territories, sized 37mm across and 11.4mm thick for an understated wrist presence when worn. One of the major changes to Grand Seiko’s bracelets fans have been crying out for is the introduction of a micro-adjustment clasp, which offers 2mm increments for enhanced comfort.
With the Spring Drive Calibre 9RB2, Grand Seiko once again proves that technical innovation need not come at the expense of aesthetic refinement. This new milestone in accuracy not only showcases the brand’s relentless pursuit of precision but also reflects its quiet mastery of design and detail. In bridging past achievements with future-forward engineering, Grand Seiko continues to define what modern watchmaking can — and should — look like.
Once you are done with this story, click here to catch up with our June/July 2025 issue.