Abstract: An apparatus detects a magnetic tag implanted in an organism as detector is moved past the organism by detecting a magnetic field difference between two positions. Prior to examination of a specimen under test, the outputs of a plurality of loops detecting magnetic fields are balanced in a uniform magnetic field. As a consequence, when one of the coils is exposed to a different magnetic field than the other of the coils this difference is detected and an alarm is sounded to indicate that the magnetic tag has been detected.

Abstract: In a method for tagging members of a large homogenous group of macro-organisms so that each macro-organism is assigned to a respective one of a plurality of statistically equivalent subgroups, successive segments of wire are cut from a continuous length of wire indelibly marked along the length thereof with a plurality of identification codes at least equal in number to the members of the large homogenous group to be tagged. Each identification code includes a plurality of longitudinally extending multidigit binary words and a circumferentially extending multidigit binary word. The circumferentially extending binary word in any identification code has one of a plurality of different values, each of the values occurring in a number of the identification codes substantially equal to the total number of macro-organisms divided by the number of the subgroups.

Abstract: In a method and apparatus for magnetizing an identification tag prior to insertion thereof into a host macro-organism, the tag is provided with a magnetic field having an orientation opposed to the magnetic field of an injection wire from which the tag has been cut. The tag and the leading end of the wire repel one another and facilitate implantation of the tag into the macro-organism by preventing withdrawal of the tag with the wire upon termination of an injection operation.

Abstract: A metallic identifying tag for allowing later identification of a non-metallic object. The identifying tag is of a circular or oblong cross-section and has a plurality of spaced grooves cut along the surface thereof. In addition, holes may be provided through the center of the tag in conformance with a predetermined pattern which thus forms a profile readily identifiable by means of x-ray equipment. In this manner, while the tag remains implanted within the object it may be inspected and the coded pattern interpreted and the history of the object containing the tag thus ascertained.