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Ballistics > Serial Number Restoration > Flashcards

Serial Number Restoration Flashcards

1
Q

What is a Serial Number?

A

A serial number is a unique sequence of numbers or letters applied to a firearm by the manufacturer for the purpose of identification.

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2
Q

The most common methods for applying serial numbers are:

A
  • Stamping
  • Laser etching
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3
Q

The three main methods for recovering erased serial numbers:

A
  • Magnetic Particle Inspection (Magnaflux ® )
  • Chemical and Electrochemical Etching Recovery Methods
  • Ultrasonic Cavitation
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4
Q

The success of any attempt to restore a serial number will depend on the following

A
  • The method that was used to apply the serial number
  • The method that was used to remove the serial number
  • The competency level of the firearm examiner
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5
Q

What may be required to know before serial number restoration is attempted?

A
  • The Examination may require disassembly of the firearm
  • The process may be destructive
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6
Q

When handling firearms these three fact should be remembered:

A
  • Firearms are weapons that are designed to kill, maim or injure.
  • Firearms carry out their function extremely well.
  • Firearms themselves do not kill or injure people, people kill or injure people.
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7
Q

What are the basic safety rules of firearms?

A
  • Always Treat all firearms as if they are loaded
  • Always point firearms in a safe direction
  • Never place your finger on the trigger unless you are ready to fire
  • Always prove the firearm when picking it up, receiving or handing it over
  • Ensure that there is an emergency eye bath nearby.
  • If you are exposed to acid you need to rinse it off your skin quickly and thoroughly.
  • Should you accidently swallow any acid drink milk and or water immediately but do not induce vomiting as the milk and or water will dilute it.
  • When mixing reagents always add acids to water, NEVER add water to acid.
  • The only way to prevent accidents is to practice safety at ALL times.
  • Examination and handling may not only involve dangerous materials but can include potentially dangerous procedures and use of equipment.
  • At all times caution must be exercised, and the use of personal protective equipment (PPE) must also be considered.
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8
Q

What is the appropriate PPE that must be worn during serial number restoration process

A
  • Activated Carbon Mask (unless Fume Hood being used)
  • Closed toed shoes
  • Lab Coat
  • Nitrile Gloves
  • Safety Glasses
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9
Q

What safety precautions should be taken when moving a Magnafux?

A

The Magnafux can be heavy, so one should exercise caution while moving it.

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10
Q

What safety equipment should be worn while using a Magnaflux device?

A

One must wear nitrile gloves, a lab coat, and safety glasses.

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11
Q

Who should not operate the Magnaflux device?

A

It is recommended that anyone with metal implants, insulin pumps, or pacemakers should not operate the device.

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12
Q

Can pregnant women use a Magnaflux device?

A

It is not recommended for pregnant women to use a Magnaflux device.

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13
Q

What is the importance of bench protection when using a Magnaflux device?

A

Bench protection should be used to protect the device and ensure optimal performance.

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14
Q

What tool is used in stamped serial numbers?

A

Stamped serial numbers are made by using a stamp.

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15
Q

How does the stamp work in stamping method?

A

The stamp uses a positive impression of a number at sufficient pressure (some 5 tons) to impart a negative impression of the stamp onto the firearm.

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16
Q

How does the Dom Matrix method work?

A

Dot matrix impressed serial numbers are made by a succession of dots and are shallow in depth.

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17
Q

How does the laser etching method work?

A

Laser etched serial numbers are made by engraving with a laser, are shallow in depth and have a burned appearance.

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18
Q

What are standard methods used by criminals for the removal of the serial number?

A

The most common methods for removal of serial numbers are:
* Centre Punching
* Drilling
* Filing or grinding
* Over stamping
* Peening
* Welding

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19
Q

What is centre punching method?

A

This method uses a pointed punch to obliterate the whole numbered surface.

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20
Q

What is the issue with centre punching?

A
  • Centre punching alters the crystalline structure.
  • It not only restores the serial number but the centre punching marks also. This marking causes an overlay of one upon the other leaves a pattern of marks which are extremely difficult to interpret into a number.
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21
Q

What is the drilling removal method?

A

This method uses a drill to remove the number and the
surrounding metal then the hole is usually filled with lead solder, epoxy or weld material

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22
Q

What is the filing or grinding removal methods?

A

This method uses a hand file, Dremel type tool or grinder with a high speed carborundum grinding wheel. Once this has been completed it sometimes is then polished and then over stamped with a new number or left as erased.

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23
Q

What is the penning removal method?

A

This method uses a round punch to hammer the surface to completely hide the number.

24
Q

What is the over stamping removal method?

A

This method uses stamping to put a new number over the old.

25
Q

What is the welding removal method?

A

This method uses either an Arc welder, Mig welder or an Oxyacetylene welder to heat and melt the surface.

26
Q

What knowledge is relevant to recover a serial number from a firearm?

A

Metallurgical knowledge and the technology of materials is relevant to the problem of recovering a serial number from a firearm.

27
Q

What is the role of line defects in the plastic flow of metals?

A

Line defects, also known as dislocations, play a significant role in the plastic flow of metals. As they move through the crystalline array of atoms, they allow the material to deform plastically rather than elastically.

28
Q

What is the difference between elastic and plastic deformation?

A

Elastic deformation is temporary and reversible, while plastic deformation is permanent and irreversible.

29
Q

How do ductile metals behave under increasing force?

A

Ductile metals will initially deform elastically when force is applied, but will begin to deform plastically when the force exceeds their elasticity limit.

30
Q

How does the behaviour of a ductile metal differ from that of a brittle metal under stress?

A

Ductile metals will deform plastically under stress, while brittle metals will typically fracture or break under stress without significant plastic deformation.

31
Q

What are other circumstances under which serial number recovery is extremely difficult or impossible?

A
  • Where serial number was produced in the item by casting (no plastic deformation) and the indentations where fully removed.
  • In metals that have been heated to a temperature high enough to cause recovery of the metal by annealing out the defects after the metal was stamped or the serial number was obliterated.
  • New numbers were stamped over the smoothed surface directly of the old numbers
32
Q

What are magnetic restoration ?

A

The Magnaflulx® technique is used by metallurgists to detect surface or
Subsurface flaws in metal.

33
Q

What are the disadvantage(s) with magnaflux?

A

A side effect of the plastic deformation created by cold-working is increased magnetism. Therefore, using the magnetic restoration method will affect the area of the obliterated serial number rather than the area surrounding it.

34
Q

What are the advantages with magnaflux?

A

Advantage of this technique is that it is non-corrosive and non-destructive.

35
Q

What metals do magnaflux work on?

A

The Magnaflulx® technique will only work on ferrous metals which are magnetic or para magentic.

36
Q

Why can ferrous metal retain magnetic field?

A

Ferrous metals that are magnetic are attracted to magnetics i.e. steel, mild steel and some steel alloys. They can retain a magnetic field after exposure.

37
Q

How are ferrous para metals be used by the Magnaflux

A

Ferrous metals that are ”para” magnetic are mainly stainless steels, whilst they will not be attracted to a magnet they can be magnetized by an externally applied magnetic field such as the Magnaflux which will form an internal induced magnetic field.

38
Q

Will ferrous metals like para metals retain a magnetic field?

A

No, they will not retain a magnetic field.

39
Q

What stainless steels are magnetic?

A

Only 304 and 306 stainless steels are magnetic.

40
Q

What is the procedure for magnetic restoration?

A
  1. Conduct a physical examination to identify any remnants of the serial number and photograph the obliterated area. Use stereo microscope to assist if necessary.
  2. Determine if the item is suitable for magnetic particle restoration by placing a magnet near the area of obliteration. It is suitable if it can be magnetized.
  3. Apply if necessary SKC-S cleaner to remove any dirt or other obscuring substance. Allow to dry before proceeding.
  4. Spray prepared bath in a beaker and allow particles to settle.
  5. Place the magnet behind the area of obliteration with the poles on either side of the area.
  6. Apply selected prepared bath to the area of obliteration with a disposable pipette or by spray.
  7. Note and photograph any characters that become visible prior to proceeding with each step.
41
Q

What is etching?

A

The metal in the region of a dislocation or in the region of localized elastic stress is more electrochemically active than the remainder of the substance, therefore it can be made to dissolve preferentially in a suitable acidic solution.

42
Q

How can you use selective dissolution to recover serial numbers?

A

By using a suitable acidic solution to preferentially dissolve the more electrochemically active metal in the regions of a dislocation or in the region of localized elastic stress

43
Q

How does cold working affect the reactivity of metal?

A

Cold worked regions of the metal usually contain more defects and therefore are more reactive.

44
Q

What is the basis for the recovery of serial numbers through etching?

A

The greater reactivity of the metal in the regions of a dislocation or in the region of localized elastic stress, which allows for selective dissolution.

45
Q

What is the procedure of chemical etching?

A

The first important step in chemical etching involves proper surface preparation:
1. Identify areas from which the serial numbers were removed.
2. Remove all dirt, debris, paint or other obscuring substances.
3. Note and record any visible characters prior to polishing
4. Polish the area of obliteration using a rotary type tool or fine grit sand paper until the area is mirror like, removing as much scratches as possible. When polishing proceed from courser to smoother paper.
5. Note any discernible characters and the position of these characters.
6. Select a chemical etchant appropriate for the type of metal.
6a. For magnetic material such as steel (listed in order of strength >):
- Fry’s Reagent
- Turner’s Reagent
- Davis Reagent
6a. For non-magnetic material such as steel (listed in order of strength >):
- Acidic Ferric Chloride
- Ferric Chloride
7. Test the strength of the chemical solution in an area adjacent to the polished area. The solution should not bubble or fizz when it comes in contact with the metal but should slowly darken due to oxidization. Dilute the chemical solution with distilled water as necessary
8. Gently rub area in one direction with cotton-tipped swab.
9. If characters appear, distilled water may be applied to the area to slow the oxidization process and allow for examination
10. Note the characters and the position these characters.
11. Continue processing until all characters are visible or it is determined that no more numbers will become visible.
12. Have the numbers confirmed by a second examiner.

46
Q

How does electroetching technique assist in etching?

A

The electroetching technique allows the etching rate to be controlled by adding an electric field to the specimen, which can speed up the etching process.

47
Q

What kind of technique is the electroetching technique oftne called?

A

This electrochemical technique is therefore an enhanced form of
chemical restoration using standard chemical etchants.

48
Q

What is the procedure for electrochemical restoration?

A
  1. Prepare the surface as with the standard etching method
  2. Using an alligator grip, apply the positive terminal to the specimen
  3. Thoroughly soak the cotton tip of an applicator with the appropriate chemical enchant and attach this to the negative terminal of the power supply via an alligator clip, being certain to do so on a moistened area at the base of the cotton tip.
  4. Wipe the area of obliteration, being careful to not touch the surface of the specimen with the alligator clip.
  5. Note any characters that become visible prior to proceeding with each step, as well as during the wiping process.
  6. Have the numbers confirmed by a second examiner.
49
Q

How can serial number on plastic surfaces be recovered?

A

Serial numbers on plastic surfaces can be restored with the application of suitable heat.

50
Q

What is a disadvantage of heat restoration in plastic surfaces?

A

A side effect of cold working of plastic is the decrease in the item’s ability to resist heat.

51
Q

When heat restoration procedure what can occur?

A

When this restoration procedure is applied, the deformed area of the obliterated serial number will be affected faster and to a greater degree than the surrounding area.

52
Q

What is the heat restoration procedure?

A
  1. Inspect the area for any trace material or other foreign substance
  2. Make note of any visible characters based on initial observations.
  3. Apply heat to the obliterated area using a high intensity lamp.
  4. Continue to apply heat until the plastic in the obliterated area begins to liquefy.
  5. Make note of any characters become visible.
  6. Have the numbers confirmed by a second examiner.
53
Q

How can restorations be classified?

A

Full Restoration, Partial Restoration & No serial number restored

54
Q

What is full restoration?

A

This is the total recognition of all the obliterated characters.

55
Q

What is partial restoration?

A

This is the recognition obliterated characters less than the total being sought.

56
Q

What is no serial number restored?

A

This is the lack of recognition of any of the obliterated serial numbers.

Ballistics (11 decks)

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