Abstract: A counterfeit detecting method and apparatus are provided for detecting the authenticity of an article having a label containing an isotope of a chemical element. The apparatus comprises a housing, a source of gamma radiation positioned in the housing, and a gamma radiation detector positioned in the housing for detecting the radiation from the source. The gamma radiation source is selected to emit radiation which can stimulate a selected nuclear transition in the label material. A calculating device, such as a microprocessor is coupled to a detector for calculating the ratio of the number of gamma rays counted by the detector during a predetermined period of time when the article is not in position near the receiving member (N.sub.O) to the number of the gamma rays counted by the detector during a period of time equal to the predetermined period when the article is positioned near the receiving means (N.sub.

Abstract: A counterfeit detecting method and apparatus are provided for detecting the authenticity of an article having a label containing an isotope of a chemical element enriched to a predetermined amount. The apparatus comprises a housing, a source of gamma radiation positioned in the housing, and a gamma radiation detector positioned in the housing for detecting the radiation from the source. The gamma radiation source is selected to emit radiation which can stimulate a selected nuclear transition in the label material. A calculating device, such as a microprocessor, is coupled to a detector for calculating the ratio of the number of gamma rays counted by the detector during a predetermined period of time when the article is not in position near the receiving member (N.sub.O) to the number of the gamma rays counted by the detector during a period of time equal to the predetermined period when the article is positioned near the receiving member (N.sub.