Grand Seiko 9R65

Grand Seiko's Spring Drive caliber combines a mechanical mainspring with an electronic regulator to achieve a perfectly smooth gliding seconds hand and accuracy of plus or minus 1 second per day. The Tri-synchro regulator uses the energy of the mainspring to generate electricity that powers the quartz oscillator and IC, eliminating the need for a battery. A 72-hour power reserve and 30 jewels make it one of the most technologically unique movements in horology.