Comptometer

(Credit Steve Bee.)

No one knows what the hell a comptometer is, but rumor has it that is was similar to a calculator - which in the the 50's was a big deal.
Link.

This machine was originally used by our Aunt Velma, and was somehow presented to her on her retirement. Odd to think of her as a working woman with an esoteric skill in the 1940's.

From what I recall, operating it required that you adapt to the machine, much like how you use an acabus, and use various strategies to do not just addition, but multiplication, division and even square roots. Speedy operators soon learned that it was faster to enter four, then five, than to reach over for the nine key.

The comptometer was a mechanically ingenious device in that you could push down several keys simultaneously to enter a number. Sums were accumulated automatically. Greater skill here led to greater speed and productivity.

That Velma even learned it was a byproduct of the Second World War era(sadly, temporary) social changes. When "the boys came home," (Steve's words) feminism, AKA humanism, took a stutter-step backwards. Our Mother and her sister-in-law returned from the workplace to become homemakers.

Still, Velma was proud of her accomplishments, and passed her comptometer along to friend Steve.

Comptometer Linky.