Abstract: Apparatus and an associated method for nondestructively determining the thickness of a coating on a metal surface, such as the interior of a can. An object securing device holds the object being inspected. The inspection device includes a probe. Positioning apparatus is employed to permit insertion of the probe into inspecting relationship which in the case of a can would involve partial insertion of the probe into the can. A first section is inspected and sequentially through relative rotational and/or translational movement of the object being inspected additional portions of the object such as can ends may be inspected. A light beam is caused to impinge upon the section of the object being inspected and returned fluorescent light received by a detector positioned within the probe cooperates with processing means to determine the coating thickness. The system permits accurate determinations of coating thickness even when the metal surface has irregularities.