Abstract: A locking device includes a key and a reading device. The key has a grip portion and a plurality of information carrier parts attached to the grip portion. The information carrier parts determine the locking code for the key. Each information carrier part is arranged to receive an information element and the carrier parts are adjustably positionable for disposing the information elements into a predetermined angular pattern. The reading device is arranged to read the locking code on the key and to compare it with a predetermined locking code for operating a lock. The information carrier parts are mounted on a member extending axially from the grip portion of the key. The carrier parts are angularly adjustably positionable about the axis of the member. The reading device contains elements for the detecting the presence or absence of the information elements in predetermined angular positions.