A borrowed ring is locked on a 4-digit combination brass lock and the dials are mixed. Your spectator can test that the lock cannot be opened. Your spectator thinks of any 4-digit number, and then dials them on the lock. The lock opens! The numbers your spectator chose are the combination that opens the lock!
Completely mechanical, and built to last. Your spectator thinks of the number, your spectator rotates the dials, your spectator opens the lock- it's that simple!
No force of any pre-set numbers!
No electronics, magnets, buttons, switches, wires, gravity switch, timers, smoke or mirrors!
Nothing is added or taken away!