A Unique Mechanical Calculator

I find the history of computing fascinating, and very often I learn a new detail about the complex evolution of how mankind adds two plus two.

So I was thrilled to discover that, for a little over two decades, a small European company manufactured a mechanical calculator weighing as little as half a pound: the Curta. It's an engineering marvel, and it doesn't use any electricity. Curta sold these interesting miniaturized devices until 1973, by which time electronic calculators had rendered even the most inventive mechanical calculators obsolete in most parts of the world. (The abacus is still popular in a few countries, and in certain specialized fields, such as aviation, analog slide calculators are still fairly common.)

I watched one Curta on eBay soar to a closing price of US$1150. Clearly I'm not the only person to find these gadgets interesting.