PROTECTION OF LEGAL DOCUMENTS BY REVERSE PENETRATION

摘要

A document has a paper substrate witb a front surface upon which information is marked in ink. The document is improved to resist alterations by erasure of selected information on its front surface. In the improvement the substrate has a back surface upon which the selected information is marked in ink in identical underlay position as the selected information on the front surface. Ink penetrates into the front and back surfaces of the substrate to such an extent in the identical underlay positions tbat the selected information on the front face may not be erased without damage to the substrate to expose ink penetration from the back surface.