Patent ID: 7802730

Claim:
An optically readable information carrier comprising: an information symbol having a predetermined area and including an optically readable mark, the optically readable mark indicating at least part of the predetermined area, the information symbol being optically readable by an information reader after the predetermined area has been identified thereby; and a mask member removably adhered on the information symbol and arranged to abut on the information symbol, and mask at least part of the optically readable mark while keeping presence of the information symbol externally visible to change the predetermined area of the information symbol to be continuously unidentifiable unless any one of the mask member and the information symbol is removed from the other thereof, wherein the information symbol has an outer periphery defining the predetermined area and a first color with a first light reflectance, the mask member is arranged adjacently around the outer periphery of the information symbol and has a second color with a second light reflectance, the first light reflectance and the second light reflectance substantially being equivalent to each other, and the optically readable information carrier is configured such that, when a frame formed with a slit whose shape and size are equivalent to a shape and size of the information symbol is removably mounted on the optically readable information carrier with the slit being aligned with the information symbol, the frame masks the mask member to expose the optically readable mark of the information symbol.