The first quartz-regulated mainspring watch (1999)

The 1999 Spring Drive as Seiko shows it in its own heritage timeline: black dial, power-reserve indicator and date. Seiko does not state the reference; the first models were SBWA001 and SBWA002 with calibre 7R68.Photograph: Seiko Watch Corporation · used with credit · Seiko heritage

The need: A mechanical watch has no battery but drifts; a quartz watch keeps time but is powered by a cell. Yoshikazu Akahane wanted a mainspring watch with quartz accuracy.
Made by: Seiko Epson at Suwa, Japan. Akahane conceived the idea in 1977, patented it in 1978 and built a first prototype in 1982; about six hundred prototypes later the watch was launched in 1999. He died in August 1998, a year before it went on sale.
What was new: The escapement is gone. A “glide wheel” driven by the mainspring turns eight times a second and generates a little electricity; a circuit compares it with a quartz crystal and brakes the wheel electromagnetically. The seconds hand does not tick at all: it glides.
Worth knowing: The first watches, hand-wound with a 48-hour reserve, were rated at one second a day. The self-winding calibre 9R65 of 2004 with a 72-hour reserve is the one most Grand Seiko owners know.
Where it is now: The Seiko Museum, Ginza, Tokyo.

Historian’s noteNot the first hybrid of mechanics and electronics: Seiko’s own Kinetic of 1988 charges a battery from a rotor. Spring Drive is different in kind, because the mainspring drives the hands and quartz only regulates the speed.

SourcesSeiko Museum · Grand Seiko