Abstract: An alteration-sensitive imprinted article made of a durable, flexible plastic sheet material has two opposing surfaces, at least one of which is capable of retaining an ink coating. A positive design is directly applied to at least a designated area of said one surface of the sheet, and at least a translucent, non-erasable film or coating or sheet composed of plastic material is bonded to and applied over at least said designated area of said one surface. The film or sheet has on the side thereof opposed to that bonded to said one surface a negative design which is exactly matched to the positive design so that the two designs comprise a blanket or continuous covering over the designated area. An erasable ink coating applied over the translucent, non-erasable film or coating or sheet covers at least the designated area of said one surface.

Abstract: This invention provides an improved process for imprinting light-transmitting, i.e., translucent to transparent, sheet material wherein the opposite faces of the sheet are initially imprinted with substantially exactly registering, mirror images. At least one side thereof, has a raised imprint formed thereon by applying a raised printing material onto the wet ink of the initial imprint, e.g., by the thermographic method.This process is especially applicable to heat resistant plastics, especially polyesters.

Abstract: This invention provides an article having an alteration-sensitive surface, generally a sheet material formed of spun continuous strands of fine interconnected fibres of polyolefin, which are bonded together with heat and pressure. The surface of the sheet material is degraded by utilizing solvents, prior to imprinting desired information onto the surface, the surface then being easily abraded so as to substantially prevent alteration without permanently changing the appearance of the surface. Preferably, the surface of the sheet material is overall coated, or imprinted, with a contrasting color such that by abrading the surface the imprint is erased and the white or other natural color of the olefin fibres appears, thus increasing the visibility of the abraded surface.