This year, prestigious Japanese watch brand Grand Seiko is celebrating its 60th anniversary. To mark this occasion, the brand announced various special edition watch models. Also this year, Grand Seiko is introducing a new generation Spring Drive caliber. In celebration of Grand Seiko 60th anniversary, Caliber 9RA5 is first presented in a professional diver’s watch, reference SLGA001.
Introduced in 1999, Spring Drive is one of horology’s greatest advances. It combines the best of both the existing two watch technologies (mechanical and electronic) in a watch powered by a mainspring that offered accuracy of one second a day. Now, two decades on, Grand Seiko introduces a new generation Spring Drive caliber that is slimmer, even more precise and has a greater power reserve.
Grand Seiko Spring Drive Caliber 9RA5
Caliber 9RA5 takes Spring Drive technology to a new level of excellence and opens a new era in the history of Grand Seiko.
In comparison to the 9R6 caliber that is the mainstay of the current collection, Caliber 9RA5 delivers a five-day power reserve, an increase of 60%. Its monthly precision rate has risen from ±15 seconds a month to ±10. The movement depth has been reduced from 5.8mm to 5.0mm and the speed of the date change has been greatly increased.
Caliber 9RA5’s thin profile is made possible by the re-design and re-positioning of the Magic Lever. Developed in-house in 1959, the Magic Lever boosts the efficiency of the automatic winding mechanism by using the energy created by movement of the oscillating weight in both directions.
In the new caliber, the new Offset Magic Lever is positioned away from the center of the movement to reduce its thickness. Remarkably, this is achieved with no loss of winding efficiency. The stem and crown are also positioned towards the back of the case to lower the center of gravity and achieve a comfortable fit on the wrist.
Caliber 9RA5 may be slim but it has enhanced rigidity and shock resistance thanks to the new layout of the gear train towards the center of the movement and a central bridge that holds them together. This One-piece Center Bridge achieves a shock resistance that meets the ISO standard for diver’s watches.
The movement incorporates two barrels which deliver a power reserve of up to 120 hours. They are different sizes so as to deliver the torque required for the five day power reserve while optimizing the use of the limited space within the movement.
Caliber 9RA5 has an accuracy rate of ±10 seconds per month thanks to a new IC package and to the selection of highly stable quartz oscillators that have gone through a three-month aging process. For the first time in a Spring Drive movement, the IC incorporates a sensor to measure the temperature within the movement and is programmed to compensate for any inaccuracies in the crystal oscillation rate which may be caused by temperature change.
The oscillator and sensor are vacuum-sealed into a single package to eliminate even the slightest temperature difference between the two and this shield also reduces the possible influence of humidity, static electricity or light interference and thus maintains the watch’s accuracy at the highest possible level.
As with every Spring Drive caliber, 9RA5’s seconds hand moves in perfect glide motion, expressing the natural and continuous flow of time that resonates so deeply with the Japanese sensibility. In its finishing, also, the movement has a beauty that is uniquely Japanese and is inspired by the natural environment of the studio where it is made.
The jewels echo the glittering stars that sparkle especially brightly during the early days of winter in the surrounding mountains and the delicate texture of the movement’s surfaces reflect the frost that winter brings to the trees.
Grand Seiko SLGA001
Powered by Caliber 9RA5, the new Grand Seiko professional diver’s watch is capable of handling the challenge of saturation diving at depths of up to 600 meters. The case is in high-intensity titanium, which is 40% lighter than steel and more impervious to scratches.
The watch has a power reserve display at the 10 o’clock position. Divided into five parts, its shows exactly and clearly how many days of power are left. The case, crystal and bezel are all designed for easy and safe disassembly for the maintenance that a professional diver demands.
The SLGA001 Spring Drive diving watch is presented in a special Grand Seiko 60th anniversary box with an interchangeable blue silicone strap. It will be available worldwide in August as a limited edition of 700.
Model: Grand Seiko SLGA001 Spring Drive, 60th Anniversary Limited Edition Professional Diver’s 600M
Spring Drive 5 Days Caliber 9RA5
Driving system: Automatic
Power reserve: 5 days (120 hours)
Accuracy: +/-0.5 seconds per day (+/-10 seconds per month)
Number of jewels: 38
Diameter: 34.0mm, Thickness: 5.0mm
High-intensity titanium case
High definition sapphire crystal
Screw-down crown, screw case back
Water resistance: 600m saturation diver’s
Magnetic resistance: 4,800 A/m
Diameter: 46.9mm, Thickness: 16.0mm
High-intensity titanium bracelet
Three-fold clasp with push button release, secure lock and extender
Approximate recommended retail price in Europe: €11,500
Limited edition of 700 pieces