The Grand Seiko Heritage Collection Series 9 SLGH005, powered by the high-beat Caliber 9SA5, is inspired by the white Shirakaba birch trees that grow near the studio in Shizukuishi. Our test examines how nature and watchmaking are reflected in this latest creation.
The word “birch” dates back to an Indo-European term that meant shiny or shimmering — describing the white bark of this distinctive deciduous tree.
Even though nothing glows on the dial of the Grand Seiko SLGH005, our test watch, by day or night, it produces a shimmering shine that was created especially for this watch. Looking at it from any angle, the prominent applied markers always catch the light, and even the smallest movement of the wrist reflects it onto the next polished surface. Reflections don’t detract from daytime legibility because the deeply grooved, highly polished markers and hands are large and distinct enough to contrast with the matte dial background. The delicate texture of the dial suggests birch bark with large and small grooves, higher ridges, and thin strips peeling away from the trunk.
In the figurative sense, the bark is peeled away a bit more at 3 o’clock where the large silver-rimmed date opening is located. The date display’s black-on-white color scheme works well with the overall appearance of the birch. The date advances instantaneously — occurring on our test watch at about seven minutes past midnight. It can be quickly adjusted using the second pulled-crown position, and the hands can be moved forward or back using the outermost pulled position without damaging the movement in any way.
The Foundation of a New Generation of Movements
The only touch of color on the dial is the slim, blued seconds hand, which advances in 10 steps each second, thanks to the high frequency of Caliber 9SA5. The delicate tip glides over the narrow dial flange with seconds and minutes markings. Pulling the large, fluted crown fully to the outer position stops the watch to allow for precise, to-the-second time setting — an indispensable feature, since the newest Grand Seiko standard specifications for the SLGH005 with the Hi-Beat Caliber 9SA5 may only gain 5 seconds or lose 3 seconds per day at most. Our test watch meets this strict standard. When we tested it on the electronic timing machine, it gained between 2.5 and 4.1 seconds per day. The watch ran even better in real-life conditions, where it deviated by only about 1 second per day.
Grand Seiko developed Hi-Beat Automatic Caliber 9SA5, first introduced in March 2020, entirely in-house over a nine-year period. According to the company, it forms the foundation of a new generation of mechanical Grand Seiko watches. The movement was first used in the gold SLGH002, which is limited to 100 pieces, at a price of $43,000. This was followed by the stainless-steel Grand Seiko 60th Anniversary Limited Edition SLGH003, limited to 1,000 pieces, priced at $9,700. Our test watch, the SLGH005, is the first unlimited production watch with the new caliber. It is available for $9,100 at Grand Seiko boutiques and select watch dealers. This is still an ambitious price when the Omega Aqua Terra, a Master Chronometer with a stainless-steel bracelet, costs $5,700, and the Rolex Datejust 36 in Oystersteel with a Jubilee bracelet is priced at $7,300.
High Frequency and Extended Power Require New Technologies
Caliber 9SA5 integrates three key developments for which several patents have been awarded or are pending: the new dual impulse escapement, the free-sprung Grand Seiko balance and the horizontal arrangement of the barrel and gear train. These mechanisms are designed for accuracy, durability and aesthetics.
In order to achieve the highest level of precision, Grand Seiko decided to begin development on a high-beat movement with a rate of 36,000 vph — a concept that the com-pany had been pursuing since 1968 with its extremely accurate Hi-Beat calibers. At the same time, a modern 80-hour power reserve was also the goal. Since both the balance frequency and the long power reserve require more energy, and the new movement was intended to be 15 percent thinner than previous Grand Seiko high-beat movements, it was necessary to redesign it from the beginning and apply new technologies. Due to the desire to reduce the height of the movement, two sequentially arranged barrels were used in place of a single large barrel. Thanks to this, and the horizontal arrangement of the gear train, the 9SA5 is now 15 percent thinner than previous Grand Seiko calibers.
High precision is also supported by the free-sprung fine regulator, which was specially developed for Caliber 9SA5. It has four weighted screws on the balance wheel, new to Grand Seiko. The square-headed screws are seated in slots (to prevent loosening), located on four inset sections of the balance wheel (to minimize air turbulence).
The balance wheel is more resistant to impacts and friction and shows a higher rate of accuracy. Contributing to this is the special Grand Seiko hairspring, which has a special overcoil and is made of a unique alloy called Spron. Its tailored design improves isochronism, i.e., uniform oscillation. The knowledge of the positive influence of overcoils on the rate of timepieces can be traced back to Abraham-Louis Breguet.
Dual Impulse Makes Power Transmission Effective
When power is transmitted to the balance wheel by the new dual impulse escapement, the escape wheel transfers the impulse directly to the balance wheel in one direction, which increases the efficiency of the entire system by 20 percent and reduces the energy needs accordingly. In the other direction, power is transferred via the pallet fork like a traditional escapement. This design is similar to the Omega co-axial escapement, although it is considerably more complex. Today, these designs are only able to be produced using modern manufacturing technologies, such as the Micro Electro Mechanical System (MEMS), which Grand Seiko has already used for earlier calibers. This process, which was adapted from microchip manufacturing, is used to produce both the escape wheel and the pallet fork of the 9SA5.
Beauty and Fine Details, Even on Hidden Parts
MEMS also allows the lightweight construction of the escape wheel and pallet fork, which saves even more energy and contributes to a higher power reserve. With this manufacturing method, first a mold is etched and then the metal is deposited into the mold using a galvanic process. This also permits another specialty of Grand Seiko: tiny recesses in the escape wheel teeth improve oil retention at trouble spots.
Even though these features are not visible to the naked eye through the watch’s sapphire caseback, Caliber 9SA5’s high frequency makes them abundantly clear. Only by stopping the watch does its extraordinary geometry reveal itself, with inset sections and angular screw heads. A sturdy balance bridge, instead of a single-sided balance cock, provides stability — a structural feature that is gaining in popularity among Swiss watch manufacturers, like Rolex, Tudor and Panerai.
The view also includes the generously skeletonized bidirectional oscillating weight and an exposed perforated bridge construction. This reveals a large part of the mechanism, like the two barrels beneath an arched bridge.
Numerous decorative finishes such as striping, perlage, sunburst finishes, polished screw heads, beveled edges, and the exquisite engraving on the winding rotor, require time and extensive effort. Even hidden surfaces of components are covered with a variety of decorations, like the mainplate filled with engraved Grand Seiko initials, which are also found on the barrel bridge, the screw-down crown and the folding clasp.
Brilliant Overall Appearance and Expression
The solid clasp completes a very attractive three-link bracelet that attaches to the case with fixed connections. It narrows toward the clasp with screwed links for an adjustable bracelet length. It is well executed with beveled edges, polished lateral surfaces and brushed upper surfaces. It continues the look of the powerful case, which has mirror-like Zaratsu polish on the narrow bezel shifting to a brushed finish on the broad case sides.
Grand Seiko designates the overall look of this watch as its Series 9 design. It is slated to become an important part of the Heritage collection in the coming years. Grand Seiko remains true to the style that was established in 1967 with the 44GS. Despite its powerful impression, the Grand Seiko SLGH005 exudes harmony, calm and stability — the same feeling you get when walking in a forest of birch trees.
Manufacturer: Morioka Seiko Instruments Inc., 61-1, Itabashi, Shizukuishicho, Iwate-gun, Japan
Reference number: SLGH005
Functions: Hours, minutes, seconds, date
Movement: In-house Caliber 9SA5, automatic, 36,000 vph, 47 jewels, certified by the Grand Seiko standard (-3 to +5 sec/day, test in 6 positions, 17 days), four regulating screws on balance wheel, Spron 610 hairspring with overcoil, Diachock shock absorber, dual impulse escapement, 80-hour power reserve, diameter = 31.6 mm, height = 5.18 mm
Case: Stainless steel, box-style sapphire crystal with anti-reflective coating on both sides (top), sapphire caseback, water resistant to 100 m
Bracelet and clasp: Stainless-steel bracelet with one-sided folding clasp with push button
Rate results (deviation in seconds per 24 hours, fully wound/after 24 hours):
On the wrist +1.2
Dial up +6.5/+6.0
Dial down +6.2/+5.2
Crown up +2.5/+0.7
Crown down +3.1/+0.9
Crown left +2.1/−0.2
Greatest deviation 4.4/6.2
Average deviation +4.1/+2.5
Flat positions 281°/ 261°
Hanging positions 262°/250°
Dimensions: Diameter = 38.87 mm, height = 12.04 mm, lug width = 22 mm, weight = 180.5 grams
Strap and clasp (max. 10 points): Attractive, nicely finished stainless-steel bracelet with sturdy, practical folding clasp 9
Case (10): High quality, well-made case with interesting alternating polished and brushed finishes, sapphire crystals and screw-down crown. 9
Dial and hands (10): Prominent markers and hands, unique relief dial design, well-matched hands 8
Design (15): The design follows the well-known 44GS with contemporary modifications; prominent numerals, hands, dial, iconic look. 12
Legibility (5): Easy to read during the day, no legibility at night; large date
display, perfect hand length 4
Operation (5): The screw-down crown is easy to grasp and loosen; screwed bracelet links for easy adjustment, secure folding clasp. 5
Wearing comfort (5): Ergonomic case and bracelet combination, comfortable despite considerable weight, attractive bracelet, sturdy clasp 4
Movement (20): Modern in-house movement with innovative solutions and unique structural features, some of which are patented; long power reserve, modern escapement, high frequency, complex and attractive decorative finishes 18
Rate results (10): Very good, especially on the wrist; complies with the Grand Seiko standards. 8
Overall value (10): Ambitious pricing compared to other similar watches, but justifiable due to the brand’s desirabilty and iconic status 8
Total: 85 POINTS
This article originally appeared in the September-October 2021 issue of WatchTime. Photos are by Grand Seiko, Marcus Kruger, and Jennifer Wunder/Pexels.