Self-verifying security documents

摘要

A security document such as a banknote 1 comprises a sheet 2 formed from a substrate bearing indicia 3 having self-verifying means. Sheet 2 has an indicia-free portion 5 of transparent plastics material. Transparent indicia-free portion 5 includes a self-verifying means including a colour tinted optical filter for viewing an area printed with metameric inks on the same or another similar security document.