Abstract: A detector device adapted to be used for detecting coins and other metal objects for various purposes including to distinguish between genuine and non-genuine or counterfeit coins, the subject detector device includes an electric tank circuit having a coil through which, or adjacent to which, an object or coin to be detected moves, apparatus to electrically shock the tank circuit to produce an output representative of the object or coin and represented as a damped wave signal the frequency and shape of which depends on the electrical characteristics associated with the tank circuit and on the physical and electric characteristics of an object or coin being detected, and a detector circuit operatively connected to the tank circuit including circuit elements connected to respond to one or more characteristics of the damped wave output.