Grand Seiko’s Spring Drive is the reference as the most accurate (mostly) mechanical movement in existence. However, in the form of a spectacular dive watch, Grand Seiko have redesigned Spring Drive for a new generation. This watch is the future of Spring Drive and the ultimate Grand Seiko dive watch. Welcome to the Grand Seiko SLGA001 60th Anniversary Professional Diver’s 600M.
Grand Seiko’s Spring Drive is perhaps the perfect watch movement. It combines the autonomy and beauty of a mechanical movement with the flawless accuracy of a quartz movement. Considering that Grand Seiko also arguably makes the best of each of those too, a combination can be viewed as the ultimate expression. However, Grand Seiko have chosen to keep innovating with the next generation of Spring Dive in the form of the calibre 9RA5 at the heart of this new dive watch.
The Ultimate Grand Seiko Dive Watch
The watch which houses this movement is a new variant of Grand Seiko’s previously High-Beat dive watches. It features a considerable size of 46.9mm by 16mm thick to offer a 600-metre water resistance. Crucially, this angular and sculptural case will not be hefty on the wrist thanks to a construction from Seiko’s own “high-intensity” titanium. This is harder than stainless steel yet is 30% lighter whilst having the superb corrosion resistance for which titanium is known.
Unlike the chequered dials of previous limited edition Grand Seiko divers, this watch has a rich, dark blue dial with the remarkable attention to detail of other divers from this brand. Perhaps the most stunning parts of this watch are the hands which resemble nothing else available and have the most stunning brushing and bevelling. The date, on this model, is displaced to 4 o’clock whilst the power reserve indicator is rotated to a somewhat awkward position at 9:30. To complement the premium nature of the watch is a smooth, glossy black dive bezel.
9RA5: The Future of Grand Seiko Spring Drive
As wonderful as this watch is (and it really is), the movement is the most important component as the herald of a new time for Grand Seiko. The Spring Drive calibre 9RA5 at the heart of the SLGA001 does not give new features, per se, but instead adds an unprecedented level of refinement.
Take, for starters, the most fundamental start of a movement’s operation: winding. As an automatic watch from Seiko, this movement uses Seiko’s ‘Magic-Lever’ which ensures unparalleled reliability bidirectional winding — usually a vulnerable component. However, due to a lack of space within a smaller movement, the system has been comprehensively revised for winding efficiency.
Now that there is power in the watch, let’s look at how the movement stores it in the Grand Seiko SLGA001. In order to reduce the thickness to only 5mm, the gear train was rearranged under just one bridge and the single, large mainspring was replaced with two smaller ones. The result is a more compact and robust movement when subjected to impacts. Additionally, the two mainsprings used don’t just match the power reserve of older movements but beats it will a full 120-hours or 5 days.
This movement isn’t simply smaller, though, as it is also significantly more accurate than previous generations of Spring Drive. The principle of a Spring Drive movement is that energy moves from the mainspring to a glide wheel which runs in a continuous motion. This powers an integrated circuit and quartz crystal which uses an electromagnetic brake both to derive energy from the glide wheel but, as a consequence, to slow it to the correct speed. In this new cal. 9RA5, the movement is thermo-compensated due to the accuracy of quartz regulation being very sensitive to temperature.
The quartz crystal itself is aged for three months and selected amongst the very best produced. Once inside the watch, it is entirely isolated for the world inside a vacuum-filled capsule. The result is accuracy within 10 seconds per month — a 50% improvement on the last generation.
Altogether, the Grand Seiko SLGA001 60th Anniversary Professional Diver’s 600M is a historically important Seiko as the beginning of something new for the brand. This is, therefore, the ultimate Grand Seiko Spring Drive.
Availability: 700 pieces for ¥1.15M (c. £8,350) before taxes
- Dimensions: 46.9mm x 16mm
- Material: “High-Intensity” Titanium
- Crystal: Sapphire
- Display: Brushed cathedral and arrow hands / Applied metal markers / Date display at 4 o’clock / Power reserve indicator at 9:30 / Unidirectional fully-graduated dive bezel with luminous pip under crystal / Seiko Lumibrite applied to the hands, markers and bezel
- Water Resistance: 600m / 2,000ft / 60 ATM
- Movement: Grand Seiko 9RA5: Time, date (with instant change) and power reserve indicator / Automatic & manual winding / Double spring barrels with 120-hour (5-day) power reserve / Accurate to within 10 seconds per month