Canon Pocketronic Versions

If you discover your Canon Pocketronic or the identical Monroe 10 you may notice some differences on the top printed circuit board. The picture below shows three different versions of the calculator.

On the left: Peter Muckermann's Canon Pocketronic
TMC1730A,TMC1731A  Date code Mid 1970 and TMC1732A Date Code Mid 1971

On the middle: Rick Bensene's Canon Pocketronic
TMC1730A,TMC1731A,TMC1732A  Date Code Mid 1971

On the right: Nigel Tout's Canon Pocketronic 
TMC1730B, TMC1731A,TMC1732A  Date Code unknown

Why that different versions of the top printed circuit board (PCB)? On the left, a machine with datecodes on the three calculating chips around 1971, the PCB holds an IC SN21893 with a date code of 1974 (!). We assume that this board does same timing corrections of the thermal printer. On the middle (Rick Bensene's machine) this IC is missing. And, finally on the right, on Nigel Tout's machine the PCB is cheap and easy. 

Do you know the difference or know other PCB's ? Please email:       

If you have additions to the above article please email:

Joerg Woerner, December 5, 2001. No reprints without written permission.