SpotlightA New Standard: The Grand Seiko Spring Drive ‘Ultra Fine Accuracy’
With an accuracy rating of +/- 20 seconds per year, Grand Seiko's new Spring Drive Ultra FIne Accuracy watches represent the pinnacle of precision watchmaking in a surprisingly practical package
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Grand Seiko have always been obsessed with accuracy. Not in the casual ‘this watch keeps pretty good time’ way, but in the ‘we’re going to spend decades perfecting this’ kind of way. Back in 1969, while most of the world was distracted by moon landings and Woodstock, Grand Seiko quietly introduced their VFA (Very Fine Adjusted) watches, guaranteeing accuracy to +/- 2 seconds per day—essentially showing off while the Swiss were still figuring out what to do about quartz. Fast forward to 2025, and they’re taking it to an almost absurd level. The new Spring Drive Ultra Fine Accuracy watches have a baffling precision rating of +/- 20 seconds per year. It’s like bringing a particle accelerator to a science fair.
Twenty Seconds Per Year
Twenty seconds per year means you’d need to wait until 2026 to notice any meaningful drift. The breakthrough in Ultra Fine Accuracy comes from the new 9RB2 calibre. Grand Seiko age each quartz oscillator for three months, test it at various temperatures, and then vacuum-seal it to prevent environmental interference. The movement takes 540 temperature readings daily to maintain precision in any condition. The famous gliding seconds hand remains, powered by a mainspring that delivers 72 hours of power reserve. Most impressively, Grand Seiko packed all this technology into a significantly smaller package than previous Spring Drive movements.
The Headliners
Two models debut this ‘Ultra Fine Accuracy’ innovation. The SLGB003 in High-Intensity Titanium will join the permanent collection, featuring a silver-blue dial that changes character with lighting conditions. For collectors, the platinum SLGB001 limited edition offers a deeper blue dial with greater visual impact. Both dials of the Ultra Fine Accuracy showcase the ‘ice forest’ pattern inspired by the frost-covered landscape surrounding Grand Seiko’s Shinshu studio.
Both watches measure 37mm across and 11.4mm in thickness—dimensions that work perfectly on most wrists. The Evolution 9 design language gives them angular cases with broad Zaratsu-polished surfaces that catch light dramatically. Bold hour markers and hands ensure the dials remain legible without needing luminous material.
The 9RB2 movement measures just 30mm across and 5mm thick, opening possibilities for Grand Seiko to use Spring Drive in more diverse case designs. Another first: a regulation switch that lets watchmakers adjust the accuracy during servicing—acknowledging that even near-perfect mechanisms benefit from occasional fine-tuning.
Perhaps equally newsworthy for Grand Seiko enthusiasts: the SLGB003 introduces a proper micro-adjustment clasp. The three-position system allows for 2mm increment adjustments without tools, finally solving the persistent bracelet sizing problems that plagued previous models.
Final Thoughts
What makes these Ultra Fine Accuracy models truly impressive isn’t just their world-record accuracy, but how they reflect Grand Seiko’s practical evolution. While chasing the seemingly unnecessary goal of +/- 20 seconds per year, they’ve simultaneously delivered what enthusiasts actually wanted: more wearable dimensions, improved functionality, and that long-awaited micro-adjustable clasp. Because when it comes to modern luxury watches, technical excellence and specification sheet dominance mean little without usability.
