The Seiko SII caliber VK63 is part of the hybrid mechanical quartz (mecaquartz) movement line. It is a chronograph movement that uses quartz technology for the main functions of the watch, and a mechanical module for operating the chronograph. Learn more here.
Time Module/Seiko states that the expected accuracy of this movement is less than +/- 20 seconds per month at normal temps. The battery life is about 3 years with normal operation.
After installing a fresh battery cell, remember to reset the circuit by touching the AC terminal of the circuit block (look for an arrow labeled AC pointing to a hole) and the switch spring with your tweezers.
The Seiko labeled caliber number for the VK63 is 6T63. You might find this caliber VK63 listed as being produced by SII aka Hattori aka TMI (Time Module Inc) aka Seiko Instruments Inc. Learn more about the different names here. Other calibers with the same base movement are VK67 and VK83.