Most cheap quartz watches from China. Add yours to the comments below.
The Seiko Instruments caliber PC21S is a 0 jewels quartz movement found in many ultra-entry level timepieces.
You might find this caliber listed as being produced by Hattori aka Epson aka TMI (Time Module Inc) aka Seiko Instruments Inc. We’re not sure why all the different names, but sure they all lead back to Seiko. Learn more about this here.
The documentation from Time Module states an accuracy of “Less than 30 seconds per month at normal temperature range.”
Replacement prices of $7.95 were found online at the time of this post.