casio personal mini

a great little calculator from around 1974. this model is cm-607.

a basic "4 banger" machine with a six digit, green vacuum fluorescent display.

interesting is the use of a special arrow key (this is not a delete button) that allows display of the next six digits of the result. the idea was to save the cost of a more expensive display but retain precision.

the display uses the half-height zero which was common in early desktop machines (eg as-8a).

for example, 123456*654321= shows 8o7798. holding the arrow key then displays 53376.o and so the answer is really, 80779853376. 11 digits, pretty neat.

the excitement stops there unfortunately because you can't chain further calculation from this result, nor can you enter numbers longer than 6 digits (eg by holding the arrow key). furthermore divide produces only a 6 figure result. eg. 1/7= gives o.14285 and holding the arrow gets the last of 6 significant figures as 7ooooo.

it is nevertheless entertaining to watch as divisions take noticeable time in calculation and the display uses the small zero `o' rather than the full sized one.

this unit came in a rather nice suede leather, stitched case. i am not sure whether this is original or whether somebody made this. i quite like it.