Serial Number – A unique number typically applied
to an object by a manufacturer
Serial Number Restoration – The practice of
restoring an obliterated serial number by using
scientific methods
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
portion of the serial number
being removed.
By removing the serial
number, criminals hope that
the object can not be
identified as having been
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 Reflection
Smooth Surface
Diffuse reflection
Rough Surface

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.
H 31 0E-06674