The recent influx of Spring Drive watches in the Grand Seiko lineup has raised speculation about Seiko’s dedication to high end mechanical movement production. However, the just released SBGH001 & SBGH003 GS watches with a new 36,000 Beats Per Hour (BPH) 9S85 caliber undeniably demonstrates that Seiko has not abandoned high end mechanical watch production. The 9S85 is a state of the art mechanical movement, and with a stated accuracy of +5/-1 seconds per day, the SBGH003 is quite possibly the most accurate mechanical wristwatch in production.
The Grand Seiko Poem
The +5/-1 seconds per day, accuracy standards documented by Seiko for the SBGH003 are the tightest I have seen published from any manufacturer today. Sure, we all have seen or heard about individual watches using various movements attaining astounding accuracy over long periods of time, but no current manufacturer that I’m aware of will guarantee their mechanical movements to be more accurate than that of the 9S85 in the SBGH003.
Although admired for their potential timekeeping abilities, super hi-beat movements do have weaknesses; most notably, increased servicing requirements and a need for a stable power flow through the gear train. From what I’ve been able to gather through translation efforts in studying the 9S85 movement, Seiko has addressed these issues through improvements in mainspring and escape wheel design.
The mainspring developed for the 9S85 is a refined version of the Spron design that we’ve seen used in Springdrive and 6R based watches. To cope with the increased power demands and minimize isochronism error, Seiko tweaked the Spron alloy and changed the mainspring dimensions to deliver a more consistent band of power throughout the 9S85’s impressive 55 hour running reserve.
Grand Seiko Mainsprings – Photograph by Seiko
Conventional escape wheel (top) and 9S85 escape wheel (bottom) photograph by Seiko
Of particular concern in a hi-beat movement is the lubrication demands imposed on an escapement working so frenetically. Through newly developed micro machining methods, Seiko has claimed improved polishing and hardening of the escape wheel teeth, and as shown above, they’ve incorporated a specialized honeycomb like design in the wheel which apparently improves the long term stability of the lubrication in the escapement. In short, the lubrication better stays where it should to keep the watch running properly.
The watch itself is very much a traditional Grand Seiko design; dauphine hands, oyster bracelet and a traditionally designed case. Many will be pleased to see that the power reserve dial, which seems to have become a popular GS complication of late, is absent.
At approximately 40mm without crown, with a thickness of 12mm, the case could be considered large for a Grand Seiko. Lug width is 20mm. The links on the oyster bracelet are held together with screws.
Seiko Shizuku-ishi Watch Studio
The dial on the SBGH003 was said to be inspired by the views outside the Shizuku-ishi watch studio. Although the dial looks black at first glance, it is actually a deep green color with textured ridges throughout. Like many green dials, it can look a little muddy at times, but in the right light, it pops. Like the dial, the markers too have tiny microscopic ridges engraved on their surfaces. The hands are polished on the sides with an incredibly fine brushing on the main surface.
As with all higher end Seikos, the casework is a wonderful combination of brushed and polished surfaces. Finishing is top notch. The screw in crown is surprisingly large.
The new 9S85 Seikos are a welcome and appropriate addition to the GS lineup. Most know that Seiko has an early history of 36,000 BPH movement design and it’s great to see that not only are they now continuing this tradition, but are also actively working on improving it through cutting edge technology and active research and development efforts.