Abstract: A credit card of electrically insulative material has electrically conductive material embedded therein. The electrically conductive material has the configuration of an irregular line extending between a pair of spaced bores in the area of an edge of the card and a plurality of spot openings in the line formed in a predetermined pattern. The credit card has openings at a surface thereof in the area of the spot openings. Each of a pair of electrically conductive annular contact members is mounted in a corresponding one of the bores in electrical contact with the electrically conductive material. A key member has a plate-like configuration of electrically insulative material having electrically conductive material spots protruding from a surface thereof in the predetermined pattern whereby when the card and the key member are juxtaposed the spots of the key member fill the spot openings of the card and close a circuit between the contact members.