Recovering obliterated laser engraved serial numbers in firearms

A survey of some metallographic etching reagents for restoration of obliterated engraved marks on aluminium–silicon alloy surfaces

“…Automobile parts have been manufactured with Al alloys instead of steel components to reduce the weight of the car. Modern firearms use high strength aluminium alloys for their frames [17,18]. More recently pin stamping, engraving and laser etching are applied for serial numbering on articles [4,19].…”

Revealing obliterated engraved marks on high strength aluminium alloy (AA7010) surfaces by etching technique

“…Some examples of cars made by these aluminium alloys are Audi A8 [15] and Honda NSX [16] and many motor cycle frames [17]. In addition many firearms like Ruger pistol [18], Czechoslavakian P-01 pistol [19], S&W Special Airweight Airlite revolver [20] and Brazilian pistols [21] use aluminum alloy frames. Ergal, a hard aluminium alloy (AA7075) is also used for manufacturing firearms [22].…”

“…They commented that the alkali by itself was an ineffective etchant, but when used after acid the contrast increased between the stamped and unstamped areas. Silva and Santos [21] used relief polishing [4] to recover obliterated laser engraved serial numbers in aluminium alloy frames of Brazilian pistols. Here the surface was manually ground or polished using abrasive papers 600, 1200 and water.…”

“…Further the engraved marks were chosen for the study, as these are currently used on many items. Also these are of similar depths as those of laser etched marks which have become now a common marking method on firearms and automobile components [9,21].…”

Restoration of abraded and covered marks engraved in steel using active infrared thermography

“…NDT methods already exploited for recovering of deteriorated marks include magnetoscopy [13] and X-rays [14]. Optical techniques, such as electron channelling contrast [15] and scanning acoustic microscope [16,17], have been employed as well.…”