Internally readable identifying tag

Claim 1

An identifying tag for implanting in small animals including fish to aid in determining the movement thereof from one habitat to another and which is identifiable by means of X-ray equipment, which comprises a solid one piece generally uniformly shaped metallic elongated member being of a length sufficiently small so as to render said member suitable for implantation into an animal, said metallic member having a substantially oblong cross-sectional shape to facilitate orientation of said tag when implanted in said animal and a longitudinal length significantly greater than the maximum cross-sectional width thereof suitable for maintaining sufficient data storage capacity on said tag, said metallic elongated member having cut in its outer surface a plurality of spaced grooves at least some of which extend only partially about the non-circular peripheral surface of said elongated member to form a predetermined fixed format binary coding system which includes an indexing means to define the reading direction of the coded grooves, said grooves being of a sufficient depth such that in profile each of said grooves is readily identifiable as being transparent as distinguished from opaque by means of X-ray equipment while said tag remains implanted in said animal.