The Pocket Counter is a simple 3-wheel counter which was made in Japan in the 1960s or 1970s aimed at the American market.
There are three small window holes on the front, each showing one number of one of the number wheels inside. The left-most number wheel can display any number from 0 to 19, whereas the other two both show a single digit. The holes are marked dollars, dimes, and cents. At the top are three buttons, and pressing a button adds one to the corresponding number. Carries occur automatically when a digit goes above 9.
There is a push button at the bottom right side which is used for clearing the register. If you press and release this button all the numbers are incremented by 2, except that they will not increment past their maximum value. To clear the register, repeatedly press and release this button until the register reads 19.9.9 and then add one by pressing the right-most button. This overflows the register so that it shows 0.0.0 again. The clearing button works this way in order to keep the mechanism as simple as possible, as it does not need to disengage the carry mechanism, nor the ratchet system that keeps the wheels from going the wrong way.
It is not clear what company produced the Pocket Counter. Other variants of these counters were made, many without clearing mechanisms.
Rechnen Ohne Strom has a page with many variants of these shopping counters.
Etsy listing for this Pocket Counter in its original packaging.
© Copyright 2016 Jaap Scherphuis, mechcalc a t jaapsch d o t net.