Jaime Hernandez: For modern coins issued from 1965 to date, the Proof 1990 No S Lincoln cent is considered a beast, to say the least. Fewer than 200 examples exist. It is from an extremely dynamic and popular series. It is the only proof coin from 1909 to date in the entire Lincoln cent series that is missing the extremely significant mint mark. The coin exists against all odds. Moreover, the missing mint mark is obvious, even with the naked eye.
In 1985 the U.S. Mint abandoned the practice of punching mint marks into working coin dies and instead, it began punching the mint mark directly onto the working hubs. However, the 1990 No S Proof Lincoln cent was inadvertently struck by a mint state die that had been processed as a proof die. This occurred because the Mint had shipped a mint state die to the San Francisco Mint without the die containing the S mint mark. Amazingly, the 1990 No S Proof Lincoln cents deceived both the Philadelphia and San Francisco Mint employees.
The 1990 No S Lincoln cents were first discovered on July 18, 1990 by Jim Gullen of New York. Following the discovery, the U.S. Mint announced publicly that several 1990 Proof Lincoln cents with missing mint marks were accidentally struck at the San Francisco Mint. The Mint also confirmed the destruction of 145 examples of the 1990 No S Proof Lincoln cents.
1990 No S Proof Lincoln cents were found in regular 1990 Proof Sets as well as being found in 1990 Prestige Proof Sets. At the time, the Mint was producing approximately 3,700 proof Lincoln cents from each pair of dies. Therefore, in the early 1990s most collectors and dealers had the notion that thousands of 1990 No S Proof Lincoln cents existed. However, time contradicted those expectations, as less than 200 coins have surfaced.
For approximately 20 years, the approximate figure of fewer than 200 coins extant has remained somewhat stable. For years, there have been no reports of the discovery of additional 1990 No S Proof Lincoln cents. The majority of 1990 Proof and Prestige sets have been inspected. Dealers, collectors and cherry pickers of both modern and classic coins are well aware of this variety, because it commands thousands of dollars even in the lowest grades. This coin is rarely encountered in any major dealer's inventory or even at major auctions, where only a few examples make an appearance each year.
The 1990 No S Proof Lincoln cent is among several other proof No S mint mark coins. These include the 1976 No S Eisenhower Dollar, the 1968, 1970, 1975 and 1983 No S dimes, and the 1971 No S nickel.