Grand Seiko Introduces the 'Ushio 300 Diver': A Highly Accurate (±20 seconds/year) and Compact Diver's Watch
Seiko Watch Corporation announces the release of the 'Ushio 300 Diver' from the Grand Seiko Evolution 9 Collection. Releasing on June 5, 2025, for 1,650,000 JPY, it features the new Spring Drive Caliber 9RB1 with an accuracy of ±20 seconds per year and the brand's smallest diver case size at 40.8mm.
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- 📰 Published: April 14, 2026 at 16:10
- 🔍 Collected: April 14, 2026 at 07:31
- 🤖 AI Analyzed: April 19, 2026 at 19:27 (131h 55m after Collected)
Seiko Watch Corporation (Representative Director, Chairman, CEO & CCO: Shinji Hattori, Headquarters: Chuo-ku, Tokyo) will release the "Ushio 300 Diver" from the Evolution 9 Collection. It achieves an ultra-high precision of ±20 seconds per year and features a 40.8mm case diameter, the most compact among Grand Seiko diver's watches. Both models are scheduled for release on Friday, June 5, with a suggested retail price of 1,650,000 JPY (tax included).
In 2025, Grand Seiko introduced the Spring Drive U.F.A. (Ultra Fine Accuracy) "Caliber 9RB2," which achieved a high precision of ±20 seconds per year, the world's highest (*1) for a mainspring-driven watch. The movement equipped in this new work is the "Caliber 9RB1," based on the 9RB2, which eliminates the date display and places the power reserve indicator on the dial side.
(*1) As of April 2026, based on our research.
Originally, Spring Drive is characterized not only by high precision but also by excellent shock resistance. A diver's watch has been born that thoroughly demonstrates the true value of Spring Drive, refining visibility, robustness, and beauty to a high degree so that it can be used with peace of mind even in sports scenes.
As the name "Ushio 300 Diver" suggests, it is equipped with a 300m water resistance performance for air diving.
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A sports watch overflowing with Grand Seiko characteristics
This work is a quintessential Grand Seiko sports watch that pursues precision, legibility, robustness, and wearing comfort at a high level. Its design is based on the "Evolution 9 Style," a design grammar that highly fuses the essence of Grand Seiko and Japanese aesthetics.
It features:
- A dial that balances visibility and originality at a high level
- A thin case with a low center of gravity
- A wide, stable bracelet
On the dial, the indexes finished with diamond cutting to catch the light and shine, the 12 o'clock index with an even greater presence for easy identification, and the clearly distinct shapes of the hour and minute hands all contribute to an effect that allows the time to be read at a glance in any situation.
A dial reflecting the tides surrounding the Japanese archipelago
Grand Seiko's brand philosophy, "THE NATURE OF TIME," expresses two Japanese spiritualities: the artisan's attitude to approach the essence of time, and the sensibility to draw inspiration from the changing of nature and seasons.
The new "Ushio 300 Diver" was named after the dynamism of the tidal currents surrounding the island nation of Japan. The dial expresses the flow of the tide with a stamped pattern and color gradation. By making the outer edge darker, the legibility of the time is enhanced, and by making the center brighter, the pattern is highlighted. Its color gradation emphasizes the flow of the tide and also brings about an effect that allows you to feel the vastness of the ocean. The blue dial of SLGB023 reflects the vast ocean pierced by sparkling light, while the green dial of SLGB025 reflects the transparency of the clear ocean shallows.
Balancing robustness and comfortable wear
By equipping it with the new, smaller, and thinner Spring Drive movement, we have achieved the most compact size among Grand Seiko's diver's watches (case diameter 40.8mm).
While following the wide "lug" design characteristic of the Evolution 9 Style, making the top surface nearly flat gives it a majestic presence on the wrist when light hits it.
The bracelet adopts a sliding lock extender system with a fine adjustment mechanism.
In addition to allowing an adjustment of 6mm in 3 steps of 2mm, it can be expanded by an additional 18mm at the extender part, assuming use in diving, allowing for a total size adjustment of 24mm. Furthermore, the crest part with the GS logo is equipped with a lock function for opening and closing the clasp, preventing the clasp from being unintentionally unlocked.
The case and bracelet utilize "High-intensity Titanium," which is about 30% lighter than stainless steel. Because it is a brighter material than pure titanium, polishing it by utilizing "Zaratsu polishing (*2)" gives it a beautifully shining characteristic.
(*2) Zaratsu polishing: A technique of pressing the case against a rotating circular surface plate to create an undistorted flat surface.