It fitted into the hand and the frame was made of metal and was quite thin. There were a series of vertical sliders, each with holes numbered 0-9. It was operated by a stylus which was inserted into the appropriate hole and then moved (I think) downwards. If the resulting figure exceeded 9 the stylus was then used to track sideways to the next column. As you can see, my memory is a bit hazy, but, hey, it was a long time ago!
As I recall, it was quite expensive so only a few people had one.
I emphasis that it was entirely mechanical (handraulic, as they say), there was no question of electrical operation.
Any help gratefully received,
David
