Abstract: An apparatus for analyzing metal alloys includes an electronic unit connected to a hand-held probe unit. The probe unit includes a radiation detector enclosed in a detector housing and a radiation source enclosed in a source housing. The detector housing is generally cylindrical in shape and has an aperture formed in its sidewall. The source housing is formed as a hollow, generally right triangular prism with an open base attached to the detector housing over the aperture and tapering to a tip having an aperture formed therein. The triangular shape of the source housing permits contact measurements in hard to get at places. A shutter drive mechanism is utilized to move a shutter means between a first position blocking radiation and a second position passing radiation from the source to the aperture in the tip of the source housing.