The SII (Seiko Instruments) caliber VK63 is part of the hybrid mechanical quartz (mechaquartz) 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. 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.
Seiko 6T63 VS VK63:
The SII caliber VK63 is essentially the same as the Seiko 6T63. The main difference is that the VK63 is produced for non-Seiko watch brands under Seiko Instruments. The 6T63 is used in Seiko branded watches such as the SSB025.
VK63 / VK63A / VK63B / VK63C:
The general/base caliber number is VK63, from the VK family of movements, with VK63A being the first version. The subsequent letter variations indicate evolution in the movements development. As of this post, only the VK63A exists, but if there are any upgrades or changes to the movement in the future, the letter will change to VK63B, VK63C, and so on.
Time Module/Seiko states that the expected accuracy of this movement is less than +/- 20 seconds per month at normal temps.
Expected Battery Life:
The battery life is about 3 years with normal operation. Using the chronograph will drain the battery faster. The 3 years estimate is based on using the chronograph for about 60 minutes per day. If you don’t use the chronograph, you may see a longer battery life. If you use the chrono frequently, you will need to change the battery sooner than 3 years.
Changing the Battery:
The VK63 takes a battery cell number 394 (SR936SW). 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.
At the time of this post, replacement prices for the VK63 were found online in the range of about $19.95 to $27.95 USD.