This year Grand Seiko debuted the first SLGW models and with them came the new caliber 9SA4, the brand’s first hand-wound hi-beat movement in over 50 years since the 45GS. The SLGW002 and SLGW003 “Birch Bark” are part of the Evolution 9 collection which is generally characterised by slimmer movements and a modern, multi-faceted case design with slim lugs. Now Grand Seiko has unveiled the SLGW004 and SLGW005. These new releases, however, belong to the Heritage Collection and are a recreation of the original 45GS from 1968.

While the case design of the 45GS was nearly identical to that of the 44GS, differing mainly in proportions, the 45GS was significant for debuting Grand Seiko’s first manually wound hi-beat 5Hz movement, the caliber 4520A. Developed by Daini Seikosha, the 45GS was launched alongside the 61GS produced by Suwa Seikosha, the brand’s first automatic hi-beat watch. While the 44GS was discontinued after only a year, the 45GS was produced for five years from 1968 to 1973, with the calibres 4520A (time-only), 4522A (time and date) and 4580A (time-only VFA).

The SLGW004 and SLGW005 essentially represents a bridge between Grand Seiko’s past and present. While it recreates the original 45GS design, right down to the Daini Seikosha logo on the dial, it houses the brand’s most outstanding modern achievement — the Dual Impulse escapement. The SLGW004 is in yellow gold and limited to 200 pieces, while the SLGW005 is in stainless steel limited to 1,200 pieces.

A faithful recreation of the 45GS from 1968

The 44GS of 1967 had a case diameter of 37.9mm and was the first manifestation of the new standard of aesthetics set by Taro Tanaka, known as the Grammar of Design. The 45GS bore the same characteristics in case geometry and finish but had slightly reduced proportions measuring 36.5mm. The new SLGW004 and SLGW005 have a case design that is faithful to the original but are larger at 38.8mm in diameter and 10.4mm high. They are also a tad larger than the SLGW002 and SLGW003 which with their modern case design measure 38.6mm by 9.95mm.

The new models retain the broad lugs and wide sloping facets of the 45GS, with a striking contrast between the satin-brushed finishing on the lug hoods and the Zaratsu-polished flanks. It has a slim bezel made up of two flat surfaces that raises it above the sloping case flanks.

The dials have a fine grained texture and the baton indexes also utilise flat surfaces and sharp angles for greater legibility. The dauphine hands, true to the original, are crafted with not two but three facets, including a finely defined centreline facet. The dial not only features the vintage Seiko logo at 12 o’clock with “GS” at 6 o’clock along with the two liner “HI-BEAT” and “36000”, but also the original maker’s mark – the Daini Seikosha lightning bolt logo, which was used to distinguish the work of the two rival divisions.

The new hand-wound 9SA4

While the original 45GS had a solid case back with a gold GS medallion, the new models have an sapphire crystal case back that shows off the new hand-wound 9SA4. The caliber is the only serially produced hand-wound high frequency movement today; at least, I can’t think of another off the top of my head.

Like the automatic 9SA5, the 9SA4 is designed with double barrels arranged in series. However, the first ratchet wheel is much smaller than the second, which is concealed beneath the main bridge. This configuration creates space for an intricate winding click shaped like a wagtail. A long, curved click spring, thicker at one end, presses the wagtail’s beak against the ratchet wheel, resulting in a distinctive clicking sound that enhances both the auditory and tactile feedback during winding.

Power reserve is 80 hours which is tracked with a power reserve indicator on the main train wheel bridge. The movement is one of perhaps only two serially produced movements that have a fairly long power reserve and a high frequency; the other being the Chopard 8Hz Calibre 01.12-C with a 60 hour power reserve. While the latter achieved this with a silicon escapement, the 9SA4 and 9SA5 achieved this with a longer, costlier route which is the invention of a brand new Dual Impulse escapement, first unveiled in the 9SA5 in 2020.

The Dual Impulse escapement adopts a hybrid impulse system. While it delivers two impulses per cycle, one impulse is given directly to the balance wheel and the other is transmitted indirectly via a lever. This design merges the robust locking and unlocking mechanism of the Swiss lever with the direct impulse action of the detent escapement, resulting in improved efficiency and long-term rate stability.

The pallet fork and lever are produced using LIGA, resulting in its intricate, skeletonized geometries that are lighter and facilitate quicker part acceleration, a crucial factor in a high-beat movement. Additionally, the balance wheel is free-sprung, and fixed under a traversing bridge for increased stability, and is paired with an overcoil hairspring featuring a proprietary curve.

The movement exhibits Grand Seiko’s approach to finishing. It is exceptionally clean and finely executed, with perlage on the base plate, striping on the bridges extending to the balance bridge, polished countersinks, and mechanically applied anglage.

The pricing strategy mirrors that of the SLGW002 and SLGW003, with the gold version priced more than three times the cost of its steel counterpart. At USD 9,700, the SLGW005 offers compelling value for a watch that is both technically accomplished and a faithful reproduction of a landmark creation in the brand’s history. In contrast, the yellow gold SLGW004 is positioned in a completely different category at USD 30,000, but it remains the more enticing option when compared to the rose gold SLGW002, which is priced at USD 45,000.

Tech Specs: Grand Seiko SLGW004 and SLGW005

Movement: Manual-winding 5Hz high-beat 9SA4; 80-hour power reserve
Functions: Hours and minutes; central seconds
Dial: Off-white/white
Case: 38.8mm x 10.4mm; stainless steel (SLGW005); 18k yellow gold (SLGW004); 30m water resistance
Availability: Limited to 200 (SLGW004) and 1,200 (SLGW005)
Price: USD 30,000 (SLGW004); USD 9,700 (SLGW005)