Grand Seiko Spring Drive watches

Grand Seiko Spring Drive is defined by its movement rather than a case design: a mainspring powers the watch, as in a mechanical movement, but a quartz crystal regulates it. Yoshikazu Akahane conceived the idea at Suwa Seikosha in 1977, and the first Spring Drive watches, hand-wound limited editions, went on sale in Japan in December 1999. Grand Seiko introduced its 9R Spring Drive movement in 2004 and makes and hand-assembles it at the Shinshu Watch Studio in Shiojiri, Nagano.

There is no escapement or balance wheel. The mainspring turns a rotor, the glide wheel, which generates a small current to run a 32,768 Hz quartz oscillator and an integrated circuit. The circuit brakes the wheel electromagnetically to hold it at eight turns per second; Grand Seiko calls this the Tri-synchro Regulator. The seconds hand glides rather than ticks. Grand Seiko rates the 9R15 and the 9R96 chronograph at ±0.5 second a day and the 9R65, 9R66 and 9R86 at ±1 second, and the self-winding calibres run for about 72 hours.

The heart of the range is the three-hand date watch of 39 to 41 mm with a power reserve indicator, on the self-winding 9R65 or 9R15, in steel, titanium, gold or platinum. The Snowflake, SBGA211, is the titanium version whose textured white dial is meant to evoke snow-covered terrain. The 9R66 GMT models add a 24-hour hand, some with a rotating 24-hour bezel, and the 44.2 mm Diver's 200 m comes in steel and titanium with a rotating diving bezel.

The chronographs use the 9R86 in a 43.5 mm case, and the 46.4 mm Black Ceramics Collection pieces combine titanium and ceramic, one of them on the 9R96 in a run of 500. The 8 Days models, 43 mm in platinum or pink gold, use the hand-wound 9R01 with about 192 hours of reserve, and the Evolution 9 SLGA007 "Lake Suwa" uses the 5-day 9RA2. The platinum SBGA385, a U.S. edition of 20, has a Kira-zuri dial, named for the ukiyo-e technique whose name means "sparkling painting".