Summary description of the Curta from Dark Roasted Blend:
* Entirely mechanical, no electricity or batteries involved.
* Designed by Curt Herzstark in 1938 and perfected inside a concentration camp.
* Considered to be the most efficient portable calculator (until electronic calculators came in the 70s)
* Simply a thing of beauty, stunning piece of engineering art.
Click the link for more backstory, or watch the Curta do its thing (brace yourself for enthusiastic voiceover action):
I want it I want it I want it. The end.