Mechanisms for joke sparking matchboxes
The two mechanisms differ in detail. The sparking matchbox joke consists of an innocent looking matchbox inside of which is one of these mechanisms. When wound up with a key and placed on the table, the motor is unable to rotate because there is a protruding piece of metal on the base of the mechanism which, when it comes into contact with the table, is forced against the motor to prevent its movement. As soon as the matchbox is picked up, the motor starts turning and sparks fly out from a flint within the matchbox.