Way back when I was at school in the 1970s, one of my classmates had a calculator of unusual design. Remember that this was the early days of pocket calculators, not long after the introduction of such classics as the Sinclair Cambridge and the HP 35. Calculators were expensive then! This particular one met an early demise when it was thrown out of an upstairs window at the school. There wasn't much left, but I did manage to rescue the keypad section, to make a control panel for a TV game kit that I built into an old black-and-white valve TV.
Many years later, I found another one on eBay:
Snazzy, isn't it? Not only is it a very early example of "landscape" control-panel design, it also has a peculiar display. The seven-segment vacuum fluorescent display is six-digit, but the calculator works with 12-digit numbers internally. The arrow key (bottom left of the keypad) shifts the display to show the other six digits of the answer. Not only that, but it also has a seven-segment font that has a half-height zero, with only four segments lit instead of the usual six.
So there we have it: the Casio Personal Mini, a quirky calculator.