Schrödinger's movement: The watch with the opaque crystal
Actually, that's not quite true. The crystal is domed saphire. But a plate of opaque metal covers the Swiss automatic movement. The movement works, as long as you move, and you can "set" the time with the crown, but you have no idea what time you're setting it to.
The company calls it a "superposition" watch (a term from quantum physics). "The time cannot be read. We do not follow the time. We take the time with us."
Do you want to be part of this piece of performance art? It's guaranteed to be a great way to start conversations with people ... who will then slowly back away from you and run. Only 2,000 euros, limited to 36 pieces.
Wikipedia entry on Schrödinger's cat: https://en.wikipedia.org/wiki/Schrödinger%27s_cat