1990 No Mintmark Proof

The 1990 No Mintmark Proof is one of the most famous error coins in the modern Lincoln cent series. All proof cents from 1968 onward were supposed to carry the "S" mintmark of the San Francisco Mint. In 1990, a small number of proof cents were struck from a die that was missing the mintmark entirely. The error was not caught before the coins were packaged in proof sets and shipped to collectors.

The discovery caused a sensation when collectors opened their proof sets and found a cent with no "S" above the date. The Mint investigated and confirmed the error. An estimated 200 to 300 examples are believed to exist, all contained within proof sets sold through the Mint's subscription program. The coin looks otherwise normal: deep mirror fields, frosted devices, sharp strike. Only the absent mintmark distinguishes it.

The 1990 No S Proof cent trades for thousands of dollars. In high-grade deep cameo condition, prices can reach five figures. Every proof cent from 1990 should be checked carefully with a magnifying glass in the area above the date where the "S" should appear. Counterfeits made by removing the mintmark from a regular 1990-S Proof do exist, so authentication by a major grading service is strongly recommended. The 1990 No S Proof stands alongside the 1968-S, 1970-S, 1971-S, and 1983-S No S proof issues in other denominations as one of the most celebrated Mint errors in modern coinage.