Grand Seiko Caliber 9RB2

Manufacturer	Grand Seiko
Caliber Number	9RB2, 9RB2A
Movement Type	Spring Drive, hybrid automatic
Diameter	30mm
Height	5.02mm
Jewel Count	34 jewels
Accuracy Rating	+/- 20 seconds/year
Power Reserve	72 hours
Rotor Winding Direction	Bi-directional (Magic Lever)
Magnetic Resistance	4,800 A/m
Hand Count	3
Functions	Central hours; central minutes; central sweeping seconds; date at 3:00
Hacking Seconds?	Yes
Other Features	Power reserve indicator (see below)
Country of Manufacture	Made in Japan
Known Models	Grand Seiko Evolution 9 Collection (Ref: SLGB001, SLGB003) (Add your watch to the comments below…)

The Grand Seiko caliber 9RB2 is a hybrid automatic Spring Drive movement found in the Evolution 9 Collection announced on April 1, 2025 at Watches and Wonders 2025. The 9RB2 is produced in the Shinshu Watch Studio in Shiojiri, Japan.

In Grand Seiko’s own words:

“The new movement achieves its ±20-seconds-per-year accuracy thanks to new and enhanced manufacturing and processing methods for the three-month-aged quartz oscillator and a newly designed IC. And, as with the 9RA series of Spring Drive movements, the frequency of each individual quartz oscillator is measured at several different temperatures, with the resulting data necessary for thermo-compensation programmed into the low-power IC. Both the oscillator and sensor are vacuum-sealed to minimize temperature differences and protect against external factors such as humidity, static electricity, and light, ensuring precise temperature adjustments and the stable performance of the quartz oscillator. In addition, for the first time in Spring Drive, the new movement features a regulation switch that can be used during after-sales service to correct any divergences in accuracy that may occur over long periods of use.” –Source

Grand Seiko claims that the 9RB2 is the “most accurate wristwatch movement powered by a mainspring today. (As of April 2025, based on Grand Seiko’s research).”

Grand Seiko U.F.A.:

The 9RB2 was introduced as a mechanical U.F.A movement, which stands for Ultra Fine Accuracy.

This abbreviation is an evolution of the V.F.A., or “Very Fine Adjusted,” a label that the brand has used as far back as 1969, for watches that were regulated to keep time within +/- 1 minute per month.

The UFA status declares that the movement is tuned to an accuracy of +/-20 seconds per year.

The rotor of the 9RB2 features text that reads: SPRING DRIVE ULTRA FINE ACCURACY

Power Reserve Indicator:

The calibre 9RB2 features a movement side power reserve indicator to keep track of the 72 hour runtime.

A look under the hood:

(Image source)

Video:

Additional Resources:

• Press-Release: A new era in the history of Grand Seiko begins with Spring Drive U.F.A. (April 1, 2025)
• Official Grand Seiko 9RB2 page
• 9RB2 user manual (pdf)