The Sharp EL-520 solar cell scientific calculator appeared in 1980, and it was made in Japan. The eighties are the age of the LCD screen, which got popular as it was cheap to produce and consumes very little electricity. So little, in fact, that it can be powered by a tiny little cheapo solar cell - which allowed for further minimisation as now, there needn't even be space for batteries.
It's 124mm high by 69mm wide, and tapers from 14 to 9mm in thickness.
This is a true scientific calculator; it has a great variety of functions, and I can imagine someone just about to take the final square root in some endless problem, only to be cast into ruin by a cloud passing in front of the sun.
This calculator likely came with a case or bag, as it has no off switch; the only way to turn it off is to darken the solar cell. I've made a little band of duct tape that can be placed around the calculator, turning it off.