The new SLGB023, which Grand Seiko calls the Ushio 300, is a strange and appealing combination: a full 300-meter dive watch built around one of the most accurate mainspring-driven movements ever made.
The Spring Drive Calibre 9RB1 inside carries Grand Seiko’s U.F.A. designation, for Ultra Fine Accuracy, and is rated to plus or minus 20 seconds per year. Not per day; per year. The case is High-Intensity Titanium, about 30 percent lighter than steel, and at 40.8mm across, 12.9mm thick, and 48.5mm lug to lug it is the smallest diver Grand Seiko has made, per the company’s own specifications. The bracelet clasp offers 24mm of total adjustment, including an 18mm diving extension. Power reserve is 72 hours, and the gradient blue dial carries the tide-pattern texture the Ushio series is named for. Retail is $12,400 USD.