The Spring Drive is a watch movement conceived in 1977 by Yoshikazu Akahane (赤羽 好和) at Suwa Seikosha (now a part of Seiko Epson after a 1985 merger). Specified to one second accuracy per day, the movement uses a conventional gear train as in traditional mechanical watches, but rather than an escapement and balance wheel, instead features Seiko's Tri-synchro Regulator system in which power delivery to the watch hands is regulated based on a reference quartz signal.
Commercially released in 1999, the movement is found in watches distributed by the Seiko Watch Corporation, including its Credor, Grand Seiko, and Prospex brands.
