Dr. Sol Taylor
The term unique means one of a kind. In numismatics that is a very sought after distinction, since the collector who owns a unique coin has no competition. In United States coins there are quite a few unique coins. And not counting grading levels, which sorts out coins by their grade, there are a number of reasonably well known unique coins.
One of the better known is the 1870S $3 gold piece. It would be worth over a million dollars if sold at auction. The 1849 $20 gold piece is also unique, but its status is uncertain since it was believed to be stolen from the U.S. Mint collection. It is illegal to own. The 1943D Lincoln cent in bronze is unique and was only recently discovered. It sold in 1996 for $82,500 - the highest price paid for a small cent. Another unique Lincoln cent is the 1974 aluminum cent. Over 1.5 million were minted, but all were melted, except for one which is now in the Smithsonian Institute and another 10-14 which disappeared in 1974 when sent to various members of Congress for their opinion and review. It is illegal to own a 1974 aluminum cent, since of the missing coins, it assumed they were taken unlawfully and therefore subject to confiscation.
The 1944S cent in zinc-coated steel (wartime composition for the 1943 cent) is another unique coin. It has been sold several times, since it was discovered around 1958 and is currently in private hands and valued at about $40,000. In 1994 Heritage Galleries of Texas bought a 1959D wheat back cent from a California collector. They sold the coin to Steve Benson for a reported $25,000, but when PCGS President David Hall examined the coin, he declared it to be counterfeit. The coin was authenticated by the U.S. Treasury Department and was later sold for a reported $20,000 to a private collector. No other 1959 (or later) wheat back cent has been discovered or reported to exist.
Another unique Lincoln cent is the 1915 cent struck on a gold planchet for the $2 1/2 dollar Pan Pacific gold piece. This coin was owned for many years by the late James McDermott, who showed it often at coin clubs and coin shows. After he passed away it was sold at least twice. The last time was for a reported $30,000. He also owned a very rare 1913 Liberty head nickel, which he also liked to show. This author saw it at the NASC convention at the Los Angeles (Statler) Hilton hotel in 1966.
Several years ago, a very dramatic 1958 doubled die cent was shown at various coin shows. The owner claimed he found it in a bag of cents and it was the only one. In 1996 a second piece was found (believed by the same person), so it was unique at one time and now may be considered semi-unique, since there are two known. Another nearly unique Lincoln cent is the 1917 matte proof cent. Around 1974 it was believed to be unique. However, since then a second piece has surfaced. Only one has been certified. So for now, it might be considered unique.
And finally, there are many unique coins among errors, since errors are not manufactured to be errors and they tend to vary one from another. One such unique coin owned by this author was a 1943S cent struck offcenter and clipped on a silver dime planchet. This triple error is unique and featured in Wexler & Flynn's Authoritative Guide to the Lincoln Cent published in 1996. So when the term unique is used to describe a very rare coin, if it is not the only one, then it is NOT unique.
Note: Dr. Sol Taylor (NASC past president, 1975) is the author of THE STANDARD GUIDE TO THE LINCOLN CENT, now in its 4th edition. Sol publishes the journal, Lincoln Sense, for the Society of Lincoln Cent Collectors (SLCC). For information contact: Sol Taylor, SLCC, 13515 Magnolia Blvd., Sherman Oaks, CA 91423.