A sheet element, such as a banknote, has an incorporated authenticating device comprising a film having at least one edge which is provided with a non-rectilinear portion or portions shaped to provide coded information relating to the sheet element. The shape and proportions of said at least one edge...http://www.google.de/patents/US4370057?utm_source=gb-gplus-sharePatent US4370057 - Method of verification of a sheet element, such as a banknote
