Improving on perfection is oxymoronic, but it’s what Grand Seiko has done with its Calibre 9RA5. The brand celebrates its 60th anniversary this year with the unveiling of a limited-edition timepiece featuring this new Spring Drive movement.
The Spring Drive is synonymous with Grand Seiko, when Seiko premiered the first iteration of the technology in 1999. The 9R65 movement, which brilliantly combined the best aspects of mechanical and quartz watch technologies, proved revolutionary.
Spring Drive Revisited
The Spring Drive movement replaces the mechanical escapement with an electric speed control mechanism called the Tri-synchro regulator. The system uses the power from the mainspring to generate electricity to power its quartz oscillator and integrated circuit (IC). In turn, the IC generates a reference signal based on the quartz crystal’s vibrations to steer an electromagnetic “brake” that regulates the speed of the glide wheel and gear train. This approach eliminates the most vulnerable components of both mechanical and quartz systems, resulting in an incredible amount of precision.
Calibre 9RA5 represents an improvement in Spring Drive technology with a slimmer design, greater precision and a longer power reserve. The movement now clocks in at five millimetres high compared to its predecessor’s 5.8 millimetres. It is also accurate to ±10 seconds a month – a rate previously matched within Seiko’s line-up only by the 9R15 movement. Finally, it also pulls ahead with its power reserve, which now sits at 120 hours – a boost of approximately 60 per cent.
The improvements in the 9RA5 are the result of three key features. First, the new “Offset Magic Lever”, Seiko’s proprietary bi-direction winding system, now sits away from the centre of the movement to reduce thickness while maintaining its famous efficiency. Meanwhile, the new IC package has a sensor to compensate for any inaccuracies in the quartz crystal’s oscillation rate caused by temperature changes. Both the oscillator and sensor are hermetically sealed within a single package to balance out temperature differentials between the two. This also helps to mitigate any environmental influences. Finally, the 9RA5’s two barrels deliver the torque necessary to create the 120-hour power reserve.
Calibre 9RA5 will make its debut in the Grand Seiko 60th Anniversary Limited Edition Professional Diver’s 600M (SLGA001). The timepiece features a sizeable 46.9-millimetre titanium case with a matching bracelet. A new one-piece centre bridge gives the watch the shock resistance needed to meet the ISO standard for dive watches.
A segmented power reserve display at 10 o’clock indicates to the wearer exactly how many days of power are left. Special L-shaped seals also ensure the SLGA001’s impermeability to helium gas, making this timepiece suitable for saturation diving.
A deep blue dial reflects the aquatic theme of the watch, with lumed hands and indices that provide excellent legibility even in murky waters. The SLGA001 comes in a special Grand Seiko 60th Anniversary box and will number no more than 700. This special offering will also include an interchangeable blue silicone strap.
True to its Spring Drive heritage, the perfectly smooth sweep of the 9RA5’s seconds hand is a sight to behold. One might say that it is the perfect representation of time’s unrelenting flow. The beauty of the movement is matched only by the SLGA001’s finishing – Grand Seiko’s famous “Zaratsu” polishing. The result is clean lines, sharp edges and a mirror-like surface here not unlike the swords wielded by samurai. While it may be true that perfection requires no improvement, Grand Seiko’s constant reimagining of the term serves as a fitting reminder of what a relentless quest for it can achieve.