As part of its 60th anniversary celebrations, Grand Seiko has introduced a new Spring Drive movement with a 5 day power reserve that debuts in a limited edition diver’s watch, the new 60th Anniversary Limited Edition Professional Diver’s 600M.
This new watch is reminiscent of the Hi-Beat 36000 Professional 600m Diver that the high-end Japanese watchmaker introduced in 2017. That mechanical diver from 2017 was Grand Seiko’s first professional diver’s watch with a depth rating of 600 meters – the brand has previously featured more recreational diver’s watches in its catalogue. The new Spring Drive diver Ref. SLGA001 has a similar case as the 2017 diver. The case is designed for saturation diving, with the valve-free helium resistance that results from Seiko innovations like an L-shaped gasket and heavy duty case construction. The grooves on the rotating bezel are extended for secure use, even with thick gloves. The five-link bracelet has a sliding extension setting to accommodate pressure changes.
The case and bracelet is made from high intensity titanium – a material that’s 40 times lighter than steel and with better scratch resistance – and measures an imposing 46.9 mm in width with a 16 mm case profile. The blue dial has highly luminous hour markers and hands to ensure optimum legibility underwater. The power reserve is at the 10 o’clock position and the indicator is divided into five parts to show exactly and clearly how many days of power are left. A date window is placed at 4 o’ clock.
The remit of the Grand Seiko team that worked on the new Spring Drive movement was simple - in size, performance and functionality, the new Caliber 9RA5 would be better than anything that came before it in the Spring Drive collection, mainly the 9R6 caliber.
The Magic Lever, developed by Seiko in 1959, and used to boost the efficiency of self-winding movements has been redesigned for us in this new movement. Here the Offset Magic Lever is positioned away from the center of the movement to reduce its thickness. 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. The movement depth has been thus reduced from 5.8mm to 5.0mm and the speed of the date change has been greatly increased.
The gear train has been moved towards the center of the movement and a one piece central bridge that holds them together and protects against shock. It also helps the movement meet the ISO standard for diver’s watches. The movement uses two barrels which deliver a power reserve of up to 120 hours, a 60 percent increase from previous movements. 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.
An accuracy rate of ±10 seconds per month (as opposed ±15 seconds on previous calibers) is achieved thanks to a new IC package. In a first for Spring Drive movements, the IC now uses 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 account for even slight temperature variances between the two, this shield also reduces the possible influence of humidity, static electricity, or light interference and thus maintains the watch’s accuracy.
A limited edition of 700 pieces, the watch is priced at $12,980.