Description
About Grand Seiko SLGB023
Grand Seiko Spring Drive U.F.A Ushio 300 Diver Evolution 9 Collection
The “Ushio 300,” a Spring Drive diver’s watch with phenomenal accuracy and a stunning blue dial
In 2025, Grand Seiko unveiled the Spring Drive Caliber 9RB2, a groundbreaking movement that received the then-new U.F.A. designation, standing for “Ultra Fine Accuracy.” Boasting an annual accuracy rate of ±20 seconds, Caliber 9RB2 earned the distinction of being the most accurate wristwatch movement powered by a mainspring.* This model is powered by Caliber 9RB1, featuring an improved construction that makes it ideal for sporting conditions while sharing the same attributes as the Caliber 9RB2.
The term ushio, which means “tide” in Japanese, evokes the waters that surround the Japanese archipelago. This creation’s blue dial reflects the vast expanse of the sea through a gradient that captures light streaming into the deep ocean.
* As of April 2026, based on Grand Seiko’s research.
About Spring Drive
Spring Drive is Seiko’s exclusive movement that achieves an unprecedented level of accuracy (+/- 15 seconds per month on average, equivalent to +/- 1 second per day) by regulating a spring-driven watch with state-of-the-art electronic technology that functions without batteries or other external power source.
As in conventional mechanical watches, the sole power source of Spring Drive is a mainspring that can be wound by the motion of an oscillating weight or by winding the crown. And just as in mechanical watches, the mainspring drives a series of gears that rotate the hour, minute and second hands. A rotor, connected to the end of these gears, generate a small electrical charge that activates an electronic circuit and quartz oscillator.
The Tri-synchro regulator is a unique speed controller for Spring Drive that replaces the escapement, which is a mechanical speed control device used in almost all conventional mechanical watches. The Tri-synchro regulator moves the second hand in a smooth motion, without ticking and with extreme accuracy.
Some 80% of the components in a Spring Drive caliber are the same as those in a luxury mechanical watch. Spring Drive is a movement powered by a spring, just like a mechanical watch, with a different kind of regulator and combines the long-lasting autonomy of a mechanical watch with the precision that, until now, only electronic watches could provide.
To ensure reliable and accurate operation, all these parts need to be manufactured to the highest standards of precision, and assembling them requires superior craftsmanship.
The development of the Spring Drive movement caliber 9R was made possible because Seiko is one of the very few manufactures with expertise in both mechanical and quartz watches.
Since the first Grand Seiko Spring Drive in 2004, new movements have been created with even more complex mechanisms–including the GMT in 2005 and chronograph with GMT in 2007. Showing that with the Spring Drive caliber 9R, time never loses momentum.
Grand Seiko SLGB023 Features
A sports watch true to the ideals of Grand Seiko
Like every Grand Seiko watch, the Ushio 300 strikes a perfect balance between function and beauty. Its legibility, durability, and wearing comfort have been thoroughly considered and painstakingly engineered to ensure uncompromising performance in any environment. Commensurate attention has been given to every aspect of the watch’s physical appearance.
The prominent indexes of the Evolution 9 Style are meticulously crafted with multiple facets. Both the hour and minute hands strike a sharply defined and powerful form, ensuring outstanding legibility at a glance.
“Ushio,” a dial that evokes the waters that surround the Japanese archipelago
The watch showcases a blue variation of the “Ushio” dial, a design theme that has been part of the Grand Seiko diver’s watch since 2022. The term ushio, which means “tide” in Japanese, evokes the waters that surround the Japanese archipelago, a timeless source of inspiration in Japan’s culture and art. Combined with a gradient design, the vivid dial color emphasizes the “Ushio” pattern while ensuring the excellent legibility for which Grand Seiko divers are renowned. The blue dial reflects the vast expanse of the sea through a gradient that captures light streaming into the deep ocean.
Enduring strength meets comfort and versatility
Thanks to the movement’s compact design, this model features a case diameter of just 40.8 mm, the smallest of any Grand Seiko diver’s watch, ensuring a comfortable fit for a wide range of wrist sizes. Both the case and bracelet are crafted from High-Intensity Titanium, a material approximately 30% lighter than stainless steel and distinguished by its bright, lustrous appearance.
Locking extension clasp with micro-adjustment
The bracelet includes a locking extension clasp with micro-adjustment. In addition to a three-step micro-adjustment that allows for up to 6 mm of fine-tuning, the extension feature, designed to be used with a diving suit, enables an additional 18 mm, for providing a total of 24 mm of adjustment.
Caliber 9RB1
The 9RB1 movement is hand-assembled by the highly skilled craftspeople of the Shinshu Watch Studio, located in a Seiko Epson facility in the city of Shiojiri in Nagano Prefecture.
While the Caliber 9RB1 shares the same attributes as the Caliber 9RB2, its power reserve indicator is located on the dial side.
Details of Caliber 9RB1
Grand Seiko SLGB023 History
Prior to 1960, to challenge the status of Swiss watches and change the perception of Japanese watches, Daini Seikosha and Suwa began the discussion of a product line that can match the quality of Swiss watches under the suggestion of the parent company. At the time, Suwa Seikosha Co. was in charge of manufacturing men’s watches, so it was decided that Suwa would be producing the first Grand Seiko (GS).
The first Grand Seiko was released in 1960, it was based on Seiko’s previous high-end watch, CROWN. This Grand Seiko has a 25-jewel, manual-winding, 3180 caliber, and only 36,000 units were produced. This was also the first chronometer-grade watch manufactured in Japan, and it was based on Seiko’s own chronometer standard.
Design style
The design language of the Grand Seiko was set in 1967, with the creation of Grand Seiko 44GS. The 44GS set the ground for all future Grand Seiko with nine elements. These elements help improve the legibility of the watch under different situations, and create a sharp, crisp visual impression:
- Double width index at 12 o’clock
- Multi-faceted rectangular markers
- Highly polished bezel
- Highly polished planes and two-dimensional surface
- Half recessed crown
- Flat dial
- Multi-faceted hour and minute hands
- Curved side line
- Reverse slanted bezel wall and case side
- Dress style with simple but beautiful design
- Zaratsu polishing
source : wikipedia
