Brand: CASIO
Model: LC-817
Type: Calculator
Picture: CASIO LC-817
Batteries: LR 44 x 2
Lifetime: Introduced: ca. 1978
Terminated: unknown
Notes: Plain calculator with a square root function and memory.

As visible on the calculator's picture, there's only an "MR"-key. That's because the "+"-key acts as an "M+="-key. The "AC"-key clears the memory.

Also noteworthy is the fact that the display shows the operator in action.

The calculator automatically shuts off after an idle period.

The calculator claims that √-9 = -3.