A medical diagnostic instrument includes a housing containing at least one battery and a light source, such as a lamp, for illuminating a medical target. A switch includes a movable member that selectively moves at least one of the battery and the lamp into and out of electrical connection with the other. The instrument is preferably fabricated from a diecast or an extrusion process wherein a thin plastic sleeve member having text and/or graphic materials can be shrink fitted onto an extruded handle.