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Methods for the Restoration of Obliterated Serial Numbers

NCJ Number
R S Treptow
Date Published
134 pages
Techniques for restoring serial numbers on metal objects are described and compared. The chemical method of restoration is judged superior because of its simplicity, relative low cost, and effectiveness.
Restoration testing was done on numbered laboratory specimens, five of ferrous and three of nonferrous metals. The metals represented those most commonly found in firearms, automobiles, motorcycles, and other laboratory specimens. Serial numbers were removed by grinding to a point just beyond obliteration. The handbook reports on the results of optimizing several restoration methods: chemical and electrolytic, ultrasonic cavitation etching, magnetic particle, and heat treatment. A brief discussion is included of the cold-frost method, radiography, liquid penetrant method, and electroplating. In addition, a step-by-step general procedure for the chemical method is presented, followed by a description of techniques for specific metals. Suggestions are offered for identifying metal alloys, recognizing styles of numerals used for serials, recording lab results, and restoring from the specimen's reverse side. Tables classify 26 manufacturers' firearms models by metal alloy used in the frame, describe the metals used in the study, and present results by method and metal type. References accompany chapters; graphic and photographic illustrations are provided.