There are different techniques for the restoration of erased marks in metals. Due to non-destructive methods are always preferred, magnetic restoration methods are generally the first-choice method. Using magneto-optical sensor-systems, as the cmos-magview, in order to restore obliterated serial numbers on vehicle identification numbers (VIN) and firearms offers a huge quality advantage compared to magnetic particle inspections and also compared to etching methods (which are not prefered at all due to their destructivity to the investigation material).

Several material examinations have been performed with steel sheets from automobiles, firearms, cast iron and stainless steel. When investigating obliterated serial numbers on vehicles, it is possible to check the VIN itself, if it was just ground off. Another big advantage is that it is possible to check with the same magneto-optical sensor system for welding seems near the VIN (see welding seams investigation for further information). Nowadays more and more vehicle identifikation numbers are not grounded off, but are cuted out and then being replaced and precisely welded into other vehicle frames.

Magneto-optical systems are perfectly suited to identify frauded as well as re-welded VINs and serial numbers on firearms. It is furthermore possible to identify re-welded plates of serial numbers with one device. Especially for car dealers the magview handheld device is neccesary in order to prevent buying stolen or manipulated cars and therefore to prevent crime support.