Abstract: A coin testing apparatus is designed to accept and test a plurality of different coins, for example some or all of the coins of a particular currency. The apparatus stops an inserted coin in a predetermined position and tests its diameter, composition and thickness. It may also test its weight. Only if an inserted coin, (or object purporting to be a coin,) passes all of these tests will it be accepted. To test the diameter, the inserted coin serves as one electrode of a capacitor. The coin rests by gravity against an inclined board of dielectric material, on the other side of which a plurality of arcuate electrodes are arranged such that, for a coin of predetermined diameter, one electrode will be opposite a position outside the periphery of the coin and another will be opposite a position inside the periphery.