each open liquor bottle in a tavern has a plastic spout with a magnetically operable valve to control the flow of liquor from the bottle . the spouts were fabricated with three integral rings extending around the spout with each ring being either plastic or metal to form a pattern that encodes information identifying a characteristic of the bottle . an annular actuator reads the pattern of rings and responds by producing a magnetic field that opens the spout valve to dispense the liquor . three rings allow up to eight different classes of characteristics to be encoded . to increase that number of classes a supplemental metal ring is attached around some of the spout adjacent to one end of the actuator when the spout is inserted therein . the actuator is modified to sense presence of the supplemental metal ring on a spout . adding another ring to certain spouts permits the number of classes of characteristics to be doubled without requiring replacement of existing spouts in a tavern .