Serial Numbers and Fingerprints Quiz 3

Question 1

Commonly Stamped Items

Answer 1

Firearms, electronics, farm equipment, machinery, and vehicles.

Question 2

Serial Number Crimes

Answer 2

Federal and state law make it a violation to alter or remove identifying data.
Theft and illegal use of items cause offenders to remove this data so ownership cannot be traced.

Question 3

Theory of Serial Number Restoration

Answer 3

Once metal has been stamped or impressed, the composition of it is changed forever due to the stress applied on the metal.
This allows for serial number restoration.

Question 4

Serial Number Definition

Answer 4

A unique number applied to an object by a manufacturer.

Unique number vary based on manufacturers by numeric or alpha characters.

Question 5

What can serial numbers tell us?

Answer 5

Date stamp of manufacturer.
Location of manufacturing.
Sequence of manufacturing.
Who the manufacturer is.

Question 6

Most Commonly Marked Items in Crime Lab

Answer 6

Firearms with obliterated serial numbers.

Question 7

Purpose of Serial Numbers

Answer 7

Quality Control: Identifies defective products.
Unique Identity: Item individuality.
Deterrent Against Theft: Assists in the possibility of recovering stolen items.

Question 8

Serial Number Application Methods

Answer 8

Can be applied by a variety of methods.
Each method imparts unique characteristics that can be differentiated from one another.
Manufacturers general use most economically efficient method for them.

Question 9

Types of Serial Number Application Methods

Answer 9

Dot Matrix Engraving.
Laser Engraving.
Stamped Engraving

Question 10

Dot Matrix Engraving

Answer 10

Shallow and are made by a rapid progression of dots.

Question 11

Laser Engraving

Answer 11

Shallow and often show a burned appearance on the metal.

Branding effect.

Question 12

Stamped Engraving

Answer 12

Most common type of engraving encountered in a crime lab.

Made using a stamp that creates a positive impression on the object.

Question 13

Plastic Deformation

Answer 13

Occurs when serial number is stamped in metal.
After force causing deformation is removed, the impression remains.
An engineering term meaning “permanent deformation” or irreversible changes due to force.

Question 14

Metal Distortion

Answer 14

Occurs due to the force or pressure applied to a surface of metal.
Depth is dependent on the strain through the surface of the metal.
Purpose of stamping is to impart a permanent impression on the metal.

Question 15

Obliteration

Answer 15

The process of making a surface or object undecipherable by wearing away.
Often occurs by grinding down most visible surface of serial number.

Question 16

Common Types of Obliteration

Answer 16

Grinding.
Pinging.
Over-stamping.
Drilling.
Welding.

Question 17

Serial Number Restoration Methods

Answer 17

Most common is chemical restoration.

Others include: Non-destructive, bar code decryption (manual), automatic decoding.

Question 18

Chemical Restoration Method

Answer 18

Uses chemical etchants (acids) on the surface of smooth metal.
Acidic ferric chloride mixture.

Question 19

Visualizing Restorations

Answer 19

Serial numbers are viewed when they are acid etched due to specular reflection and diffuse reflection.

Question 20

Specular Reflection

Answer 20

The ability to view the light reflecting off a smooth surface.

Question 21

Diffuse Reflection

Answer 21

The ability to view light reflecting off a rough surface.

This dark area that reveals number is result of diffuse reflection.

Question 22

Steps in the Restoration Process

Answer 22

1. Polish the surface (provides specular reflection and a consistent reflection of light.
2. Apply acid which will react with metal and produce hydrogen gas bubbles.
3. Documentation

Question 23

Rinse and Repeat

Answer 23

Acid etching may restore serial number the first time, but if not the step can be repeated.

Question 24

Serial Number Restoration Documentation

Answer 24

Accomplished by:
Extensive note-taking.
Chemicals used.
Order of operations.
Photographs.

Question 25

Decryption of Barcode Identifiers

Answer 25

Step by step process for restoring obliterated serial barcode identifiers using conventional processing and automatic decryption methods.

Question 26

What is a Barcode?

Answer 26

Series of patterned bars and spaces of at least 2 different widths.
Encryption into a computer text of a legible serial number.

Question 27

Arrangement and Sequencing of Barcodes

Answer 27

Denote alpha/numeric/symbolic characters converted to a computer text.

Question 28

History of the Barcode

Answer 28

Development begain in 1948.
First application by railroad industry.
1981 accepted Barcode 39 for by DOD for items sold to military.

Question 29

Code 39 Specifications

Answer 29

Fixed pattern of elements that represent single character.

All codes include one start and stop character in addition to serial number characters.

Question 30

Code 39 Characters

Answer 30

Each character has 9 elements, 3 of which are wider than the others.
9 bars = 1 character.
1 character = 5 dark bars and 4 light bars.

Question 31

Code 39 Symbols

Answer 31

43 character choices:
0-9, A-B, *$/+%-
Start and stop characters always an asterisk.

Question 32

Interpreting Barcode

Answer 32

9 elements = “W & N” pattern.

Bar pattern will correspond with a character denoted in the Code 39 Key.

Question 33

Steps for Automatic Decoding

Answer 33

1. use Code 39 barcode reader.
2. Scan barcode.
3. Must have complete barcode.
4. If portions of bars are missing, take a picture and fill in bars, then scan again.

Question 34

Chemical Restoration of Barcodes

Answer 34

Use chemical etch method with low corrosive rate.
If successful, manually decrypt for quality assurance.
If partially successful, attempt to scan with code 39 reader or manually decrypt.

Question 35

Techniques for Restoring Barcodes

Answer 35

Automatic Decoding.
Chemical Processing.
Manual Decryption.

Question 36

Steps for Manual Decryption: Step 1

Answer 36

1. Inspect barcode and make sure you have portions of each bar.

Question 37

Steps for Manual Decryption: Step 2

Answer 37

2. Determine if all bars are present.
   Know structure: 7 characters.
   One character = 5 dark bars.
   Have total of 45 dark bars.

Question 38

Steps for Manual Decryption: Step 3

Answer 38

Separate Character Units.
Start at left and count 5 black bars.
Place line in space between black bars.

Question 39

Steps for Manual Decryption: Step 4

Answer 39

Count wide and narrow patterns for each section.

Question 40

Steps for Manual Decryption: Step 5

Answer 40

Use code 39 key.
Find corresponding W or N pattern on chart.
Determine each character.