Grand Seiko just claimed the accuracy crown. The new UFA (Ultra-Fine Accuracy) movement achieves ±20 seconds per year. Not per month. Per year.
That’s staggering for any watch using a mainspring.
How They Did It #
Spring Drive already bridges mechanical and quartz worlds. A mainspring powers the movement, but a quartz oscillator regulates the timekeeping through an integrated circuit and electromagnetic brake.
The new 9RB2 caliber takes this further. The quartz oscillator itself has been redesigned for better stability. Temperature compensation is more sophisticated. The IC is now visible through the display caseback - previously it was hidden due to environmental sensitivity concerns.
To fit the enhanced components, Grand Seiko went from two barrels to one. Power reserve drops from 5 days to 3 days. That’s the trade-off for hitting ±20 seconds annually.
The Watches #
Three models at launch, all premium pieces.
The steel SLGA025 and SLGA027 run around €12,000. Platinum SLGB001 pushes toward €50,000.
All feature 40mm cases with the new easy-adjust bracelet clasp that collectors have wanted for years. Grand Seiko finally listened on that one.
Context Matters #
±20 seconds per year means the watch deviates by about 0.055 seconds daily. For reference, COSC certification requires ±4 to ±6 seconds per day. Rolex’s Superlative Chronometer demands ±2 seconds per day.
The UFA is 36 times more accurate than COSC standards. That’s not incremental improvement. That’s a different category.
Who Needs This? #
Practically speaking? Nobody. ±2 seconds per day is already more accurate than most people can perceive without instruments.
But accuracy has always been watchmaking’s most fundamental pursuit. Grand Seiko just pushed the boundary further than anyone thought possible with a mainspring-driven watch.
The engineering alone justifies attention. Whether it justifies €12,000 depends on your priorities.