This is the head of a mechanical numbering machine. The ratchet pawl pictured advances the numbers with each stomp on the foot pedal. The machinery also re-inks the stamps, rotates the ink pad to fresh ink, and performs the actual stamping with each cycle. The whole thing is really, really neat. I'm saving it - one day I want to number a limited edition series of something with it.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.