Abstract: Playing cards that include a machine-readable bar code in the form of a number of mutually parallel and juxtaposed bars, wherein the code is adapted to be read by light sensitive detectors. Each playing card includes at least one six-position binary code in which a bar is either present or absent at each of the six positions. The code includes a reference code in the form of an additional bar in at least one further position adjacent to the six-position binary code. The reference code is positioned for detection by a light sensitive detector. The binary code is intended to be read by means of the light sensitive detectors when the existence of the reference code is detected.