Grand Seiko

Evolution 9 Spring Drive U.F.A. Ushio 300 Diver SLGB023

Name: Grand Seiko Evolution 9 Spring Drive U.F.A. Ushio 300 Diver SLGB023 SLGB023
Brand: Grand Seiko
SKU: SLGB023

Ref. SLGB023

2026–present · 40.8mm · caliber Grand Seiko Cal. 9RB1: Spring Drive, self-winding with manual-winding, 72h PR, 33j; U.F.A. accuracy of ±20 seconds per year, power-reserve indicator

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Movement tier: unclassified · caliber Grand Seiko Cal. 9RB1: Spring Drive, self-winding with manual-winding, 72h PR, 33j; U.F.A. accuracy of ±20 seconds per year, power-reserve indicator · 72h power reserve (3 days)

Medium-large: suits wrists 6.5 in+ (16.5 cm+)

40.8 mm case. 21 mm lug width. Wears confidently on average to larger wrists. May overhang on slender builds.

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Authentication

Grand Seiko is counterfeited far less than the Swiss names it competes with, and a 2026 titanium diver on a movement nobody else makes is not a practical fake target. The checks worth doing here are about the Spring Drive behaving correctly and the titanium being what it should be.

Known issues in the market

A Spring Drive seconds hand GLIDES. It does not tick and it does not sweep in the eight-beats-a-second way a mechanical does. A seconds hand with any visible step is not a working 9RB1, and that is the single fastest check on this watch.
This is the U.F.A. specification, rated to plus or minus twenty seconds a YEAR. A watch drifting seconds per day is not performing to specification and needs Grand Seiko, not a general watchmaker.
High-Intensity Titanium is harder than the grade 5 titanium most brands use, so it should not show the soft scuffing plain titanium picks up. Unusually easy marking is worth questioning.

Area	What to check	What is correct	Red flag
dial	Seconds hand motion	A continuous, entirely smooth glide with no perceptible step at any magnification	Any stepping or stutter, which means the glide wheel is not running as a Spring Drive should
dial	Power reserve indicator against actual running	Indicator tracks toward full on winding and the watch runs roughly 72 hours from full	An indicator that sits at one end regardless of winding, or a reserve well short of 72 hours
case	Unidirectional bezel and its ceramic insert	Turns anticlockwise only, through 120 defined clicks, with the colour fired through the ceramic	Bidirectional rotation, a click count that does not reach 120, or a different colour showing at a chipped edge
crown	Screw-down crown against the 300m rating	Threads and seats cleanly; the diver rating depends on it entirely	Cross-threading or a crown that will not seat

Common legitimate replacements

Bracelet links and the diver extension are ordinary service items.
The ceramic bezel insert is replaced after damage; ceramic chips rather than scratches, so damage tends to be obvious.

Expert resources: Grand Seiko service can confirm the reference and is the only realistic route for a Spring Drive regulation problem. The caliber 9RB1 is new in 2026, so an independent watchmaker is unlikely to have parts.