SII/TMI Caliber PC21J

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.

Labeling:

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.

Accuracy:

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).

Replacement Prices:

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.

Watch Movement Specifications and Drawings:

Additional Resources:

• Official TMI tech sheets/drawings (pdf)