A hand-cranked desk mechanism to watch. For anyone who likes desk objects that do something: turn the hand crank and watch the comet pin catch a slot, advance the six-station orbit one crisp 60-degree step, then pause before the next pass. A hands-on curiosity for a desk, shelf, or workbench.

How it works. Turn the hand crank and the 1.4 inch comet drive wheel spins; its comet pin sweeps into a slot on the 1.8 inch six-station Geneva wheel, pushes the orbit forward exactly 60 degrees, then clears free so it locks in place until the next pass. One full crank turn advances the comet six times.

What it is built from. Four parts make the machine: a flat base, a hand-crank knob, a slate-blue comet drive wheel carrying the comet pin, and a white six-station Geneva wheel with six radial slots. The crank knob tops the drive wheel; both wheels turn on posts fixed to the base, pin meeting slot with each pass.

Finish and fit. The drive wheel surface is dotted with small round craters, and six raised pegs mark each station on the orbit wheel. Pin meets slot with a fine 0.03 inch clearance, tight enough to catch cleanly, loose enough to release smoothly, finished with the crisp, fine layer lines of a precision print.