NGC Authentication Techniques & Tools 2 — Questions and Answers
Question 1: Which tool is most commonly used to measure the specific gravity of a coin to detect base metal forgeries?
- Hydrostatic scale (Correct answer)
- Digital micrometer
- Electromagnetic spectrometer
- Ultrasonic thickness gauge
Correct answer: Hydrostatic scale
A hydrostatic scale measures specific gravity by comparing a coin's weight in air versus water, revealing whether the alloy composition matches genuine coins.
Question 2: When examining a coin under a microscope for die characteristics, what does 'die polish' typically appear as?
- Raised flow lines on the fields
- Random scratches across the design
- Fine parallel lines in the coin's fields from polishing the die (Correct answer)
- Pitted surfaces on the high points
Correct answer: Fine parallel lines in the coin's fields from polishing the die
Die polish lines are fine parallel lines visible in a coin's fields that result from the mint polishing the die surface, not the coin itself.
Question 3: What is the primary purpose of X-ray fluorescence (XRF) analysis in coin authentication?
- To detect artificial toning applied to surfaces
- To determine the elemental composition of the coin's metal (Correct answer)
- To measure the exact diameter of the coin
- To identify die varieties by mapping relief
Correct answer: To determine the elemental composition of the coin's metal
XRF analysis bombards a coin with X-rays and measures the resulting fluorescence to identify the elemental composition of the metal non-destructively.
Question 4: A coin exhibits mushy, indistinct lettering in the legend but sharp design elements in the center. This pattern is most consistent with:
- A genuine coin struck with a worn die
- A cast counterfeit where the mold captured detail unevenly (Correct answer)
- Authentic mechanical doubling from the striking press
- A coin cleaned with an abrasive substance
Correct answer: A cast counterfeit where the mold captured detail unevenly
Cast counterfeits often show uneven detail reproduction because the casting process captures fine lettering at the edges less precisely than central design elements.
Question 5: Which characteristic best differentiates a 'whizzed' coin from a genuinely uncirculated example?
- Whizzed coins have heavier weight than originals
- Whizzed coins show artificial luster with a grainy, directional texture under magnification (Correct answer)
- Whizzed coins always display removed mintmarks
- Whizzed coins have altered edge reeding patterns
Correct answer: Whizzed coins show artificial luster with a grainy, directional texture under magnification
Whizzing involves mechanically buffing a coin's surface, producing an artificial sheen with a distinctive grainy or directional texture visible under magnification unlike genuine mint luster.
Question 6: In detecting altered dates on U.S. coins, which technique provides the most reliable evidence of tooling?
- Weighing the coin on a precision scale
- Examining digit edges under high magnification for tool marks and disturbed metal flow (Correct answer)
- Checking the coin's magnetic properties
- Measuring the coin's diameter with calipers
Correct answer: Examining digit edges under high magnification for tool marks and disturbed metal flow
High magnification reveals tool marks, disturbed metal flow, and inconsistent digit depths around altered numerals that cannot be hidden by the counterfeiter.
Question 7: What does 'environmental damage' refer to in NGC's grading and authentication standards?
- Damage caused during coin transportation
- Surface deterioration from exposure to reactive chemicals, humidity, or improper storage (Correct answer)
- Scratches caused by mishandling at the mint
- Wear caused by decades of normal circulation
Correct answer: Surface deterioration from exposure to reactive chemicals, humidity, or improper storage
Environmental damage refers to surface problems caused by external factors such as PVC contamination, chemical exposure, salt air, or reactive materials that cause pitting, corrosion, or staining.
NGC Authentication Techniques & Tools 2
Which tool is most commonly used to measure the specific gravity of a coin to detect base metal forgeries?