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The Seiko Instruments caliber PC21J is a no jewels quartz movement found in many entry level timepieces. Although these movements are marked “Japan”, they are assembled in Japan and not entirely made in Japan.
Some of the topics covered in this caliber listing:
You might find this caliber listed as being produced by Hattori aka Epson aka TMI (Time Module Inc) aka Seiko Instruments Inc. Learn more about this here.
Official documentation claims that the accuracy of the Cal. PC21J is less than +/- 20 seconds per month when operating under normal temperatures. Normal temperatures for this caliber would be a range between -5C to +50C (23F to 122F).
PC21J VS PC21S:
There is a similar caliber PC21S with the main difference being that the PC21J discussed on this page has a longer battery life of 3 years, compared to 2 years for the S model. Another big difference is the average accuracy of +/-20 sec/month (PC21J) compared to +/-30 sec/month (PC21S).
At the time of this post, replacement prices for individual PC21J movements were found online for $6.95 USD. They are also available in bulk. For example, you can buy a lot of 10 of these movements for $29.99 USD.