Seiko Sii Tmi Caliber Pc21j Drawings

SII/TMI Caliber PC21J

Seiko Sii Tmi Caliber Pc21j Drawings

Manufacturer Hattori aka Seiko Instruments Inc. (SII) aka Time Module (TMI)
Caliber Number PC21J
Type Quartz
6 3/4”’ x 8”’
Diameter 18.5mm
3.15mm thick (overall height 4.8mm)
Battery Cell Number SR626SW
Frequency 32,768 hz
Quartz Type Tuning fork type quartz crystal
Stem 354222 / tap 10
Hand Sizes 1.20mm / .70mm / .17mm
Jewels 0
Hands count
Functions Central hours, central minutes, central seconds
Country of Manufacture Singapore
Known Models Many cheap quartz watches from China. Add yours to the comments below.

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.


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).


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:

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