System for authenticating an object on the basis of certain physical phenomena or character, specifically, measurable, but not practicably duplicable random variations in the object. In one form, the object (authenticator (T)) is a paper tag having a reference space (14), the varying translucency pattern of which is a measurable but practicably unduplicable characteristic of the paper. The reference space (14) is sensed to provide reference signals indicative of the varying translucency. A reference numeral (10) is then provided from some registered form, as on the tag or in a list. If the numeral (10) is readily accessible, it likely will be cryptographically encoded. Note the value of putting encoded information on the tag to avoid the need for large reference files. For verification, freshly sensed reference signals, as from the tag (T) (actually characteristic of the tag) are compared with signals that previously were sensed as characteristic of the tag (T). Structures are disclosed as specific forms of the authenticator (T), along with apparatus for authenticator production, detection and manipulation. Different forms of tags (210) are disclosed, the measurable characteristic of which involves light transmissivity and reflectivity. Apparatus (111) for spectrographic confirmation of tag material is also disclosed. In an illustrative form of a tag (T) as an identification means, tags and processing apparatus utilize magnetic medium (218) and printed images (214). The magnetic medium (218) is also disclosed to be recorded as for developing information on shelf life and sales channels.