CrunchGear

Apologies to our friend from the Seattle meetup who hates steampunk; this was too great to pass up (and not strictly steampunk). This wonderful little machine was state-of-the-art in 1903, when it was used for adding up columns.

That’s really all it can do; it has no functions other than addition because the mechanism is so simple and elegant, each paddle shifts a gear a certain amount corresponding to the numeral being added, and the aggregate of all the shifts is recorded up to 999. It’s even got a “clear” button. More photos and a more in-depth explanation of the mechanism here.
[via Retro Thing]