Serial Number Restoration – The practice of restoring an obliterated serial number by using scientific methods

Serial Number – A unique number typically Serial Number – A unique number typically applied to an object by a manufacturer applied to an object by a manufacturer

Serial numbers can be applied in a variety of methods. Each method has unique characteristics which enable them to be differentiated from each other.

Dot matrix engraved serial numbers are fairly shallow and are made by a succession of dots

Serial numbers engraved with a laser are shallow and have a “burned” appearance.

Stamped serial numbers are made by using a stamp with a positive impression of a number and applying sufficient pressure to impart a negative impression of the stamp on the object

The compressed area at the base of the stamping is strained below the surface of the stamp mark

When serial numbers are obliterated, they are generally ground down beyond the lowest point of the original stamping.

This results in the visible This results in the visible portion of the serial portion of the serial number being removed.number being removed.

By removing the serial By removing the serial number, criminals hope number, criminals hope that the object can not be that the object can not be identified as having been identified as having been stolen.stolen.

The serial number is no longer visible due to the removal of the top layer of the metal.

The area below the obliterated layer is affected by the stamping process and is the reason serial number restoration is possible.

Serial numbers appear when they are acid etched due to specular reflection.◦ Specular reflection – light reflecting off a smooth surface◦ Diffuse reflection – light reflection off rough surfaces

Specular Specular ReflectionReflection

Diffuse Diffuse reflectionreflectionSmooth Smooth

SurfaceSurface

Rough Rough SurfaceSurface

An obliterated serial number typically has a surface that has been scratched so that the number is no longer recognizable

The first step in the process of restoring the serial number is to polish the surface by using sand paper in progressively finer grits.

Polishing the surface will help in visualizing the serial number.

Acid Etching – The acid reacts with the metal and produces hydrogen gas bubbles

The result of the acid etching is a restored serial number. The dark appearance of the numbers is the result of diffuse reflection.

An ATV was suspected of having been stolen from a local dealership.

When police attempted to read the VIN (Vehicle Identification Number) it was observed that it had been obliterated.

The number in question was located on the engine

The surface with the obliterated number was located on the top of the engine block

This is the area on top of the engine where the VIN number was stamped.

The first step in the restoration process will be to sand it smooth.

After the surface was sanded, Acid was applied to the engine block.

The Vehicle Identification Number was restored to H310E-06674. Using this information, police were able to verify the ATV was stolen and press charges against the suspect.

HH 0033 11 --EE 00 66 66 77 44