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Today many of the manufactured items such as firearms, automobiles, motorcycles, & bicycles are impressed with a serial number for purposes of identification. In an attempt to hide the identity of the numbered item, the numbers are often obliterated or removed by mechanical methods such as grinding (Photo 1), peening, and punching.

Photo 1 - Serial Number Destruction Attempt

Serial numbers are usually stamped on a metal frame or plate, with hard steel dies. These dies are applied with enough force to sink each digit into the metal. Restoration of obliterated serial numbers can many times be accomplished, using several different recovery methods, because the metal crystals under the stamped numbers are placed under a permanent strain.  Recovery methods can include examining magnetic properties (Photo 2) or the use of a chemical etchant (Photo 3). When a suitable etching agent is applied, the strained crystals will dissolve at a faster rate as compared to the unaltered metal, thus permitting the etched pattern to appear in the form of the original numbers.

Photo 2 – Magnetic

Photo 3 - Etching

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