Seiko/Credor Spring Drive

The design of the Spring Drive's movement drew on original Epson technologies and included a groundbreaking mechanism. This limited-edition watch was first sold in 1999 under the Seiko and Credor line, Seiko's luxury watch brand. It was hand-wound and spring-driven like a mechanical watch, yet it was controlled by a crystal resonator for outstanding, quartz-like accuracy.

While the power source and train were identical to those used in mechanical watches, the Spring Drive was accurate to within a monthly rate of +/- 15 seconds (equivalent to a daily rate of +/- 1 second) and featured a sweep second hand.