NGC Authentication Techniques & Tools 3 — Questions and Answers
Question 1: When authenticating ancient coins, what is the significance of 'die axis' measurement?
- It confirms the metal purity of the coin
- It measures the rotational relationship between obverse and reverse dies, which can indicate period and mint (Correct answer)
- It determines whether the coin has been cleaned
- It measures the diameter accuracy of the flan
Correct answer: It measures the rotational relationship between obverse and reverse dies, which can indicate period and mint
Die axis measures how the obverse and reverse designs align rotationally, and consistent die axis orientation can help authenticate coins by matching known mint practices of the period.
Question 2: A suspected counterfeit Morgan dollar shows correct weight and diameter but the reeding appears slightly irregular. What is the most likely explanation?
- The coin is genuine but was struck with a defective collar die
- The coin is a cast counterfeit finished with artificial reeding (Correct answer)
- The coin was worn on the edges through circulation
- The coin had its date altered after minting
Correct answer: The coin is a cast counterfeit finished with artificial reeding
Cast counterfeits often display irregular reeding because counterfeiters must add or simulate the edge reeding after casting, making it difficult to exactly replicate the uniformity of genuine collar-struck reeding.
Question 3: Which feature of a coin's luster helps numismatists determine if it was struck with fresh dies versus late-state dies?
- The color temperature of the luster
- The flow line intensity and completeness radiating from the design elements (Correct answer)
- The thickness of the coin's edge
- The presence or absence of bag marks
Correct answer: The flow line intensity and completeness radiating from the design elements
Fresh dies produce sharp, complete flow lines radiating from design elements into the fields, while late-state dies show weakened or incomplete flow lines due to die wear affecting metal flow during striking.
Question 4: What is 'thumbprinting' in the context of coin authentication?
- A technique for identifying die varieties by their unique marks
- Residue or oils from fingerprints etched into a coin's surface that can cause long-term damage (Correct answer)
- A method of marking authenticated coins for registry
- The process of recording die fingerprints in authentication databases
Correct answer: Residue or oils from fingerprints etched into a coin's surface that can cause long-term damage
Thumbprinting refers to fingerprint residue that has chemically etched into a coin's surface, often visible as permanent marks that can affect grade and sometimes mimic artificial toning.
Question 5: How does NGC use population reports in the authentication process?
- To set market prices for coins
- To track how many examples of a coin have been certified, helping identify unusually high submissions of rare dates (Correct answer)
- To determine the minimum grade for certification
- To record the physical measurements of certified coins
Correct answer: To track how many examples of a coin have been certified, helping identify unusually high submissions of rare dates
NGC population reports track the number of coins submitted and certified at each grade, and a sudden surge in submissions of a rare date can be an early warning sign of counterfeiting activity.
Question 6: A coin shows cartwheel luster when rotated under a light source. What does this confirm about the coin's surface?
- The coin has been artificially re-toned
- The coin retains original mint luster with intact flow lines from striking (Correct answer)
- The coin has been professionally cleaned and re-lustred
- The coin was struck from proof dies
Correct answer: The coin retains original mint luster with intact flow lines from striking
Cartwheel luster is produced by unbroken flow lines from the striking process reflecting light in a rotating pattern, confirming that the coin's original mint surface remains intact.
Question 7: Which authentication concern is specific to early American large cents compared to later copper coins?
- Large cents are more susceptible to magnetic alteration
- Large cents have numerous documented die varieties that counterfeiters replicate, requiring attribution expertise (Correct answer)
- Large cents cannot be authenticated by weight alone
- Large cents are commonly found with added silver plating
Correct answer: Large cents have numerous documented die varieties that counterfeiters replicate, requiring attribution expertise
Early American large cents have hundreds of documented die varieties catalogued by specialists, and counterfeiters sometimes create false rarities by altering common die varieties to resemble scarce ones.
NGC Authentication Techniques & Tools 3
When authenticating ancient coins, what is the significance of 'die axis' measurement?