This is a well made pocket trick in solid brass. The magician asks a spectator to load any number of the steel balls into the cannon and screw the cap down. The magician can then instantly tell how many of the steel balls have been placed in the cannon. As the instructions say: No magnets. No Weights. No Compass. No Extra Gadgets. It is self operating, yet can be examined under a microscope. The Davenport advertisement is also illustrated.