In one embodiment, a method for manufacturing an identification document is provided. The method includes: providing a substrate constructed and arranged to receive printing thereon; printing a first variable indicium on the substrate, where the first variable indicium is not visible to the human eye...http://www.google.com/patents/US7798413?utm_source=gb-gplus-sharePatent US7798413 - Covert variable information on ID documents and methods of making same
