A security document such as a credit card or the like carries an automatically, machine-sensed material adapted to generate reproducible signals unique to such document. The material is arranged randomly along a line-like track and sensed by a scanning head having a transverse sensing slot of much greater...http://www.google.com/patents/US4982073?utm_source=gb-gplus-sharePatent US4982073 - Token such as a credit or identification card and an apparatus for testing the token or card
