** WARNING more tech-heavy content than usual, for nerds only or those on strong stimulants **

While Seiko has been busy celebrating the 55th Anniversary of their ďDiverísĒ via Prospex with the release of the holy TRINITY, the brandís 60th anniversary celebrations have been left in the very capable hands of their upper echelon label, Grand Seiko who has released a new GS Spring Drive Diver Ė namely the GS 60th Anniversary Limited Edition Professional Diverís 600M ref. SLGA001.

The watch or at least the movement that powers it, has been engineered to be: slimmer, more precise and more powerful than ever, boasting a new Spring Drive movement, the Caliber 9RA5 which will surely carry the Spring Drive Diver into the next decade.

Before the Spring Drive came along, you could either chose a mechanical watch with its traditional character and autonomy and relative lack of precision or you went Quartz giving you up to ten times the accuracy but at the same time the necessity for a battery; not to mention the not so elegant jumping secondís hand.

Seiko came up with the solution to this quandary more than two decades ago. In 1999, they released the Spring Drive combining the best of both movement technologies in a watch powered by a mainspring that offered an accuracy of one second per day.

Twenty years on, Grand Seikoís Spring Drive remains one of their greatest innovations. However two decades is a long time so we should expect a substantial leap in technology which is exactly what the new Caliber 9RA5 offers over the outgoing 9R6.

Seiko say of the new generation Caliber 9RA5 that it takes Spring Drive technology to the next level offering enhancements in every aspect of its performance and finish. It is also slimmer more precise and offers an even greater level of autonomy.

By comparison the Caliber 9RA5 delivers a five-day power reserve over the 9R6, an increase of 60%. Its monthly precision rate has risen from Ī15 seconds a month to Ī10.

Thanks to what Seiko call the ďOffset Magic LeverĒ the movementís depth has been reduced from 5.8mm to 5.0mm all the while maintaining the same high degree of winding efficiency in addition to the speed of the date change being greatly increased. Tbh they had me at magic lever!

The caliber 9RA5ís thin profile is made possible by the re-design and re-positioning of said Magic Lever which was developed in-house as far back as 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.

For the new caliber, the ďOffset Magic LeverĒ has been positioned away from the center of the movement reducing its height.

This was achieved without the loss of any winding efficiency. The stem and crown are also positioned towards the back of the case to lower the center of gravity and achieve a more comfortable fit on the wrist. So I wonder if this means this GS Diver actually has a slimmer case?

The Caliber 9RA5ís new slimmer figure also boasts enhanced rigidity and shock-resistance thanks to the new layout of its 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 ISO standard for diverís watches.

The movement incorporates two barrels (one large and one small) that 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.

So how about the extra monthly Ī5 seconds over the 9R6? The caliber 9RA5 achieves its accuracy rate of Ī10 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 maturing process. Not sure what the heck IC stands for, sorry!

The new generation Spring Drive movement, for the first time incorporates an IC 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 watchís accuracy at the highest possible level.

As with any Spring Drive caliber, the 9RA5ís second hand moves with the same elegant, ultra-smooth gliding motion.

The movement has a uniquely Japanese aesthetic inspired by the surrounding nature outside of the studio where it is made.

The jewels are supposed mirror the sparkling stars in the winter skies over the mountains while the delicate texture of the movementís surfaces represents frost on the winter trees. It all sounds very nice, but how about it diving attributes, I hear you ask.

As a testament to just how capable it is, the first timepiece to be powered by the Caliber 9RA5 is a professional diverís watch. It has Helium and water-resistance so that the watch could be taken on a SAT (saturation) dive to a depth of up to 600 meters.

The case has been crafted from high-intensity Titanium, which is 40% lighter than steel and more impervious to scratches. The power reserve is at the 10 oíclock position and the indicator is divided into five parts to show 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.

SLGA001 is presented in a special Grand Seiko 60th anniversary box with an interchangeable blue silicone strap. It will be available worldwide as of August as a Limited Edition of 700 pieces. MSRP in the EU is 11,500Ä.

Thoughts? Grand Seiko never fails to impress nor does the Spring Drive; itís an impressive piece of kit and Iím a huge admirer of the GS Diverís Pro 600m but just not enough to ever buy one.

But even if I was inclined and had eleven and a half thousand euro burning a hole in my pocket - 11 and a half grand!!! Come on! Itís nice but not that nice Ė is it? What do you think?