(Received 20 November 1973; accepted 21 January 1974)
Published Online: October
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Serial numbers on stolen property or guns are often removed by filing or grinding. On recovered property it is necessary to restore the numbers sufficiently so that they may be read or photographed before they can serve as evidence. In recent years aluminum and metals other than iron and steel have been increasingly used for vehicles, tools, firearms, etc . Several restoration methods exist for each of these types of metals, but they involve chemical , magnetic, dye penetrant, or heat treatment methods. Also, each method is usually unique for the type of metal being examined, and many of these methods allow the numbers to show up only temporarily, with great skill being required to gain the needed photographic evidence. Furthermore, the specimen usually requires a series of mechanical and chemical treatments such as grinding, polishing, and etching, before the numbers can be seen. These treatments all run the risk of losing any residual traces of the numbers due to the restoration technique itself.
Materials engineer, Lewis Research Center, National Aeronautics and Space Administration, Cleveland, Ohio
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