Grand Seiko 60th Anniversary SLGH002 with New Hi-Beat Calibre 9SA5 and Dual Impulse Escapement

We didn’t expect anything less. To celebrate its 60^th anniversary, Grand Seiko launches its new hi-beat mechanical calibre 9SA5, the foundation stone for an entirely new generation of Grand Seiko watches. Representing an advancement as revolutionary as the first calibre 9S of 1998 – the base movement powering all watches in the Grand Seiko (barring Spring Drive) collection to date – the new 9SA5 maintains the high-beat frequency but extends the power reserve and adds an extremely rare Dual Impulse Escapement. Making its inaugural voyage onboard the newly designed yellow gold time-and-date Grand Seiko 60^th Anniversary SLGH002, the watch will be available at Grand Seiko boutiques in August 2020.

Raising the stakes with the 9SA5

The challenge for Seiko’s development team was to deliver the same level of stable accuracy found in the existing high-beat 36,000vph movement (the 9Sxx hi-beat family) but extend the power reserve from 55 hours to 80 hours and slim down the movement. To achieve this, three fundamental structures were redesigned from head to toe using a combination of precision manufacturing tools, the time-honed adjustment skills of the watchmakers at the Grand Seiko’s Studio Shizukuishi and innovative technical solutions.

Dual Impulse Escapement

Developed entirely in-house, the new escapement wheel transmits power directly to the balance improving efficiency (hence the 80-hour power reserve for a high-frequency caliber). The novelty here is the dual impulse escapement – a very rare and impressive technical solution. In one direction, power is transmitted directly to the balance, in the other it is via the pallet fork, as in a traditional escapement. With this technology, the locking and impulse functions are dissociated – a solution presenting similarities with the Audemars Piguet or the Omega Co-Axial escapements, for example.

Micro-electromechanical system technology (MEMS) was used to craft the pallet fork and escapement wheel with its eight star-shaped arms (teeth) and tiered tips. Thanks to the ultra-precision machining technology, these vital components are machined to tolerances of one-millionth of a gram and are 5% lighter than others, meaning less power is required to turn them.

Grand Seiko Free-Sprung Balance and horizontal gear train

The Grand Seiko Calibre 9SA5 is equipped with a new free-sprung balance that is more resistant to shock and friction and retains its precision for longer periods. Calibre 9S, for example, relies on a flat hairspring: the new 9SA5 uses an overcoil. To achieve the optimal shape for the overcoil, more than 80,000 simulations were undertaken in the lab.

The new calibre is 15% slimmer than the current 9S Grand Seiko high-beat calibre and has a height of just 5.18mm. This was achieved with an innovative horizontal layout of the barrel and gear trains. The two barrels are arranged in sequence to extend the power reserve from 55 to 80 hours. Finally, the balance is held in place by a transversal bridge – again something new for Grand Seiko, which ensures greater stability and shock resistance.

The movement is finished in meticulous Grand Seiko style but also introduces new, more demonstrative design codes than in past watches. The gentle curve on the bridges is meant to evoke the outline of Mount Iwate and a bend in the Shizukuishi river that can be seen from the windows of the watchmaking studio. Also, the oscillating weight is more open than before, allowing for a better view of the movement. The stripes decorating the bridges appear less “industrial” and add a haute horlogerie finish to this calibre 9SA5, alongside the blued screws and the generously bevelled bridges. This new movement has a lot of charm.

New case design

The new calibre 9SA5 makes its debut inside the Grand Seiko 60^th Anniversary Limited Edition SLGH002, an 18k yellow gold watch with a slightly larger case size of 40mm (39.5mm for 9S) but a much slimmer profile of 11.7mm (13mm for 9S). Entirely redesigned, the case now features wider lugs for enhanced comfort. However, the main difference can be appreciated in the leaner silhouette of the case and the gentle camber that allows it to sit perfectly on the wrist. As with all Grand Seiko models, the case finishing is superlative with its mixture of brushed surfaces – including the flat part of the bezel and the curved sides of the case –  and the vivid, distortion-free, mirror-polish finish (Seiko’s legendary Zaratsu technique).

Abiding by the rules laid down for the Grand Seiko Style in 1967 with the famous 44GS, legibility is perfect. Other distinguishing elements include the more prominent and thicker hour markers in 18k yellow gold (faceted and polished) and the larger hour hand, both features of the first Grand Seiko of 1960. The date, sitting underneath the gold bevelled frame, changes instantly.

The watch comes with a brown crocodile strap with an 18k yellow gold three-fold clasp.

Availability and price

The Grand Seiko 60^th Anniversary SLGH002 is a limited edition of 100 pieces. It will retail in Europe for EUR 45,000 and will be available in August 2020 at Grand Seiko Boutiques. For more information, please visit grand-seiko.com.