Making Moderns column from Sept. 14, 2015, issue of Coin World:

In the whole of U.S. bullion coinage produced from 1986 to date, only five issues can be found with prooflike surfaces: the 2015-W American Liberty, High Relief gold $100 coin; the 2009 Saint-Gaudens, Ultra High Relief gold $20 double eagle; the 1994 and 1995 American Eagle 1-ounce gold $50 bullion coins; and the 1986 American Eagle silver bullion coin.

Prooflike versions of the bullion issues are not produced deliberately. Most often U.S. bullion coins are minted with a Matte or Satin Finish surface, but when they have a deeply reflective surface, they are called “prooflike.” 

During grading, to determine if a coin is prooflike, graders will hold an object, usually a finger, above the coin’s surface. To qualify for the prooflike designation, the reflected image will need to be sharp throughout the entire field area on both obverse and reverse. Contrary to popular belief, sharpness of the image is more important than depth when judging the quality of reflection, as these coins have concave fields that do not reflect from great distance.

At first glance, prooflike bullion coins are immediately recognizable because they appear dark. This stark difference in appearance is one reason they are valuable. The other is rarity. Just one in 10 of the 2009 Saint-Gaudens, Ultra High Relief double eagles is prooflike.

While a certified Mint State 70 coin trades for under $2,500, an example graded MS-70 prooflike sells for $5,000. 

The rarity is more extreme for the newly issued 2015-W American Liberty, High Relief gold coin, where just one coin in 40 is prooflike. Currently these coins are trading for three times the price of their nonprooflike counterparts.

The other three issues are considerably scarcer. Numismatic Guaranty Corp. has certified 83 examples of the 1986 American Eagle silver bullion coin as prooflike, out of 122,000 coins of that issue that NGC has certified! 

Additionally, NGC graded 17 prooflike examples of the 1994 American Eagle 1-ounce gold $50 bullion coin. Almost all were discovered in 2006, in a single Mint box of 1994 American Eagle gold coins and are considered to be among the most deeply mirrored of all prooflike bullion coins.

Last and rarest, NGC has certified just two prooflike examples of the 1995 American Eagle 1-ounce gold $50 bullion coin. 

No public trades are reported for the 1994 or 1995 issues. Their mystery and rarity adds to their allure.

More from CoinWorld.com:

Where did they come from and why do they exist?: Shady stories for U.S. coins

Enhanced Uncirculated 2015-W Native American dollar in 2015 American $1 Coin and Currency set

Consider collecting Coronet gold $5 half eagles: Q. David Bowers

Why the modern world coin third-party-graded market is growing

Part of £1.3 million Anglo-Saxon coin hoard discovered in 2014 going on display: Coin World Buzz

Keep up with all of CoinWorld.com's news and insights by signing up for our free eNewsletters, liking us on Facebook, and following us on Twitter. We're also on Instagram!