San Francisco photographer Kevin Twomey shot an amazing gallery of images of the inner workings of a large collection of mechanical calculating machines from the collection of Mark Glusker, stitching together multiple images to ensure that every rod, gear and linkage was vividly rendered.
Glusker, a mechanical engineer who designs medical devices for Novartis, has one of the most impressive calculator collections around. It began in 1995 with a hand-cranked digital Curta he calls "a beautiful piece of precision machinery." He inherited it from family friend Dr. A.L. Patterson, the pioneering X-ray crystallographer. He has since accumulated about 100 more. They were made in Germany, Denmark, Sweden, Italy and the United States, between 1961, when the first electronic desktop calculator was introduced, and 1971, when manufacturers stopped producing mechanical calculators completely. Most were purchased online for about $30, though some were given to him by people eager to be rid of them.
The Surprising Complexity of Old-School Calculators [Jordan G Teicher/Wired]