A Review from Hodinkee:
Introducing The Grand Seiko 60th Anniversary Limited Edition Professional Diver’s 600M SLGA001, With New Spring Drive Caliber 9RA5
Spring Drive technology from Seiko has had a long and sometimes arduous history. The technical story begins in the late 1970s, when Yoshikazu Akahane came up with the original idea, and by the time the first Spring Drive was released in 1999, the development effort had produced over 200 patents and many hundreds of prototypes. The first automatic Spring Drive movements came out in 2005 and since then, Spring Drive has appeared in everything from chronographs, to dive watches, to extremely elevated chiming complications. It has also appeared very much dressed for the ball, in Credor and more recently, Grand Seiko watches. For sheer diversity of expression, it is equaled by few other movements.
Grand Seiko has just announced the next step in the evolution of Spring Drive technology: the new caliber 9RA5. It seems to be a bit of theme this year for performance upgrades launching in Grand Seiko watches, as we’ve just seen with the new Hi-Beat limited edition, with the caliber 9SA5. 9SA5 is a thinner version of the Grand Seiko Hi-Beat, with an 80-hour power reserve, and the new caliber 9RA5 likewise offers an extended power reserve of up to 5 days, or 120 hours – in a movement 0.8mm thinner than the current 9R65 caliber and which is more tightly regulated as well. The launch platform for the new movement is a new diver’s watch, with a 600 water-resistant “high intensity titanium” case: the SLGA001 Professional Diver’s 600M.
This will be the deepest-diving Spring Drive Pro Diver from Grand Seiko – the two current Spring Drive dive watches, SBGA231 and SBGA229 are both rated to 200 meters, with the 600 meter rating reserved for the mechanical SBGH255 which also has a soft iron dial and is antimagnetic to 16,000 A/m. Spring Drive is in many respects an ideal technology for a dive watch – you have quartz watch accuracy, without dependence on batteries (it’s always worth remembering that Spring Drive watches are powered by a mainspring). The new SLGA001 is, not unexpectedly, a burly creature of the deep, at 46.9mm x 16.0mm, but the use of titanium for the case and bracelet should do much to reduce the perceived bulk. Professional dive watches from Seiko generally avoid helium release valves – instead the seals and gaskets are designed to prevent helium gas intrusion in the first place, which is true of the new SLGA001 as well. This makes the watch suitable for use by professional saturation divers.
The new caliber 9RA5 incorporates a number of enhancements to the self-winding Spring Drive movements. It seems to be an objective for Grand Seiko to have the potential to produce thinner watches, and while the SLGA001 is a thick watch, the caliber 9RA5 incorporates some changes in construction to allow for a flatter profile.
One of these, according to Grand Seiko, is a slight re-positioning of the Magic Lever away from the center of the movement, which allows it to sit flatter under the winding rotor. The Magic Lever system is something of a signature feature of Seiko watches; it’s been around in one form or another since 1959 and is a remarkably simple, robust mechanism.
The gear train has also had its layout tweaked and now lies along the central horizontal axis of the movement under a one-piece central bridge. The result is stronger construction and better resistance to shock.
The longer power reserve is courtesy of two mainspring barrels which lie in the same plane in the movement (again, this helps keep the movement relatively flat). The two barrels are asymmetrical in terms of size, which allows them to fit in the available space while still offering maximum bang for the buck in terms of energy delivery.
Finally, the quartz timing package, which controls the rate of rotation of the Spring Drive glide wheel, now features temperature compensation – again, according to Grand Seiko, this is a first for any Spring Drive movement. Temperature compensation is via a thermal sensor, which is in the same hermetically sealed package as the quartz crystal, in order to ensure the temp reading exactly matches the ambient temp affecting the crystal. Accuracy is improved to ±10 seconds per month maximum deviation from rate, over ±15 seconds per month for a standard Spring Drive caliber.
The new movement is a very interesting development. As with Seiko movements in general, Spring Drive calibers have tended to be on the robust side, with more thought given to reliability and sturdiness than to reducing height. At 5.0mm thick we have, in the 9RA5, a Spring Drive caliber which approaches the height of some classic purely mechanical workhorse movements. The ETA 2825, for instance, is 4.8mm thick, to pick just one example.
The SLGA001 is a limited edition of 700 pieces globally and it’s a precision-made piece of high-end horological engineering, designed to keep Grand Seiko’s tool watches at the cutting edge of horological innovation.
Brand New March 2021! Complete Grand Seiko Limited Edition Box Set with all books, Warranty Papers, Additional Brand New GS Blue Rubber Strap, Hang Tag, Polishing cloth, etc! Super Limited Edition with the Newest 5 Days GS Movement…Limited Edition #644/700 with warranty through March 2024!!
BRAND: Grand Seiko
MODEL: 60th Anniversary Professional Diver 600 Limited Edition SLGA001
MOVEMENT: Spring Drive – Cal 9RA5 – 5 Days (120 hours) Power Reserve
CASE: High Intensity Titanium
CROWN: Screw Down Crown
DIAL: Grand Seiko Anniversary Blue Dial
BEZEL: Rotating Diver
CONDITION: As-New! Warranty dated March 2021! – Extended warranty until March 2024!
BOXES/PAPERS: Complete Grand Seiko Limited Edition Box Set – comes with everything as shown in pictures!
WATER RESISTANCE: – 600m
STRAP/BRACELET: – 2 – Original Grand Seiko Titanium Bracelet with all links & Additional Brand New Grand Seiko Blue Rubber strap with buckle.