A card embodying the invention includes marks which are randomly formed within a dedicated region of the surface of the card. The randomly formed marks may, for example, include; (a) partial-holes extending a short distance from a surface of the card; (b) through-holes extending between the top and bottom surfaces of the card; (c) burn marks, or (d) ink marks. The marks are of a size and nature such that they are not readily visible to the naked eye. The invention includes illumination apparatus for illuminating the card to reliably sense the optical pattern of the randomly formed marks. In accordance with one aspect of the invention, a reader/writer includes apparatus for generating an array of light to uniformly illuminate the back surface of the card so as to pass light through the through-holes or through the partial holes. In accordance with another aspect of the invention, a reader/writer includes a light source for illuminating the front surface of the card containing the randomly formed marks and projecting the light onto the dedicated region of the card at an acute angle and sensing apparatus for capturing the light signals reflected from the random marks while ignoring the light reflected from the portion of the card not containing a mark.