Grand Seiko 60th Anniversary Limited Edition SLGH003
The Grand Seiko 60th Anniversary Limited Edition SLGH003 features a bold dial and a 40mm stainless steel case. However, the pièce de résistance is the new Calibre 9SA5, a high-frequency movement rich in technical attributes.
In March 2020, as part of its 60th anniversary celebrations, Grand Seiko released the SLGH002. This model, housed in 18-carat yellow gold and measuring 40mm in diameter exudes luxury from every facet of its case. The dial indicates the hours, minutes, seconds and date, all with lucid efficiency. However, from a personal perspective, as beautiful as this watch is, it is the movement in this timepiece that excites me the most. Now, the same movement, the Calibre 9SA5, features within a new watch, the Grand Seiko 60th Anniversary Limited Edition SLGH003, sharing a similar specification, save for its stainless steel housing.
The Calibre 9SA5 is a new high beat movement for 2020. The balance has a frequency of 5Hz, beating 10 times per second. Although Grand Seiko has been producing its 5Hz Calibre 9S85 since 2009, this latest movement, the Calibre 9sA5, delivers more, much more.
In terms of high-frequency movements, they deliver superior precision, are less susceptible to shocks and are less prone to positional errors when worn. However, they do have potential downsides. If you read my article on the Grand Seiko 60th Anniversary Limited Edition SLGH002, you will discover that the Japanese marque has surmounted such technical challenges. Furthermore, having made the Calibre 9S85 for over 10 years without any adverse feedback, Grand Seiko has shown it has mastered high-frequency movements where other brands have struggled.
Most mechanical movements feature a Swiss lever escapement. It is the escapement which controls the flow of time, causing the indications to advance at the desired speed. Unfortunately, this type of escapement is not very efficient. The new Calibre 9SA5 features a dual impulse escapement. When the balance wheel rotates in one direction, it receives an indirect impulse, similar to a Swiss lever escapement. However, unlike a Swiss lever escapement, when the balance rotates in the opposite direction it receives a direct impulse. This approach mitigates energy consumption, enhancing the power-reserve.
In common with most mechanical watches, the Calibre 9S85 is fitted with an index-adjuster. With this system, moving the index adjuster towards or away from the stud, alters the effective length of the hairspring, thereby adjusting the rate. In terms of the Calibre 9SA5, it is equipped with a far superior variable inertia balance, sometimes termed a ‘free-sprung’ balance. In this instance, the effective length of the hairspring remains constant. Four timing screws positioned on the rim of the balance wheel can be tightened/loosened, changing the moment of inertia, making the movement run faster or slower. With this approach, the regulation of the watch should remain within tolerance for longer.
Grand Seiko has shown its obsession for the tiniest of details. For instance, by positioning the four timing screws ‘in-board’ i.e. not projecting beyond the rim of the balance wheel, less air turbulence is produced, further aiding precision. Furthermore, the hairspring is endowed with an overcoil, this causes the hairspring to breathe concentrically, enhancing isochronism and, by default, precision. The free-sprung balance is less susceptible to positional influence, ensuring greater consistency of rate when the watch is held in different positions.
Grand Seiko has reduced the thickness of the Calibre 9SA5 by 15% when contrasted with the Calibre 9S85. This has been achieved by positioning the gear train at the same height as the twin barrels, bestowing the movement with a slimmer profile.
By housing the Grand Seiko 60th Anniversary Limited Edition SLGH003 in a stainless steel case, the model proves far more affordable than the gold SLGH002. However, rest assured the movement within the SLGH003, the Calibre 9SA5, shares the same sublime specification as its costlier gold sibling.
Approximate recommended retail price in Europe: €10,000 (13.10.2020)
The brand’s press release
First revealed in March 2020, 9SA5 is an entirely new high beat mechanical movement. Developed from scratch exclusively for Grand Seiko, Caliber 9SA5 will be the foundation upon which a whole new generation of Grand Seiko mechanical watches will be created. Nine years in development and deploying all the skills and experience that Grand Seiko has gained over the past 60 years, 9SA5 is without doubt the finest mechanical calibre Grand Seiko has ever created. Today, a new addition to the 60th anniversary collection provides a perfect showcase for this revolutionary calibre. With a stainless steel case and a dial in a deep, shimmering blue, this new creation will be available in December in a limited edition of 1,000 at Grand Seiko Boutiques and selected retailers worldwide.
The three innovations that set Caliber 9SA5 apart
9SA5 has a precision rate of +5 to –3 seconds a day and a power reserve of 80 hours and yet is 15% slimmer than the current Grand Seiko high beat calibre. The precision, power and slimness of Caliber 9SA5 are the result of the radical re-design of three key structures, and components within them, for which several patents are either already granted.
1. The Dual Impulse Escapement
The escapement is entirely new and was developed in- house. It enables the escapement wheel to transmit power directly to the balance, leading to a significant energy transfer efficiency increase. It is unique in that, in one direction, power is transmitted directly to the balance while, in the other direction, it is via the pallet fork, as in a traditional escapement. Both the pallet fork and the escapement wheel are made using MEMS technology.
2. The Grand Seiko Free-sprung Balance
9SA5 uses a new free-sprung balance, again developed especially for this calibre. It retains its precision for longer and is more resistant to shock and friction. While other 9S calibres uses a flat hairspring, 9SA5 uses an overcoil, whose curved shape was decided after more than 80,000 simulations, with the result that its performance is optimized in every possible position. Its unique design improves the isochronism.
3. The Horizontal Gear Train
The new calibre is 15% slimmer than the current Grand Seiko high beat calibre, thanks to the innovative horizontal layout of the barrel and gear trains.