The application discloses a security mark consisting of a plurality of layers, of which the cover layers are highly conductive films and the layers of the card core are films of varying transparency. One layer carries information, which can be read directly, if desired, above a security print, while the transparent conductive layer has an additional security markings, such as biometric or product identifiers marking which can be read conductively only with the aid of a special reader. All the layers consist of polymers, papers or mixtures which can be fused together to form a laminate which is fused together. The conductive layers form conductive traces which may be formed with single-walled or multi walled nano tubes or they can be formed from multiple layers or dispersions containing, carbon nano tubes, carbon nano tubes/antimony tin oxide, carbon nano tubes/platinum, or carbon nano tubes/silver, carbon, silver or carbon nano tubes/silver-cloride. An alternative layer can be formed from a separate conductive layer or suitable dispersion and the encoding accomplished by overlaying a nonconductive trace.