1870-S

The 1870-S half dime is the most famous unique coin in the Seated Liberty series and one of the greatest rarities in American numismatics. Exactly one example is known. Mint records carry no mintage figure for the coin. Research by Nancy Oliver and Richard Kelly established that San Francisco Mint officials filed paperwork for coins of all current denominations to be placed in the cornerstone of the new San Francisco Mint building during its 1870 construction. That paperwork is the only documentation of the 1870-S half dime's existence, and the cornerstone ceremony is the most plausible explanation for why the coin was struck at all.

The single known example was discovered in early 1978, not in an advanced collection or a museum but in a junk box of common type coins at a Chicago-area dealer. The dealer sold it as an ordinary half dime, unaware of what it actually was. The new owner recognized the date, authenticated the coin, and brought it to public attention at the 1978 American Numismatic Association Convention in Houston that August. It was the only coin missing from the Louis Eliasberg Collection, and Eliasberg had died two years before the discovery, never knowing the coin existed.

The first sale transferred the coin to Michigan dealer John Abbott for $425,000, a price reportedly calculated as the hammer price of the famous John Work Garrett 1804 silver dollar plus $25,000. From there it passed through additional hands, eventually reaching collector Bob R. Simpson for $1.4 million, who later sold it privately to Tom Bender. At the Bender Family Collection sale at Heritage in January 2023, the coin (graded MS64 by PCGS) sold for $3,120,000, the current auction record for any half dime.

The 1870-S half dime exists as a legendary numismatic object rather than a collectible. No collector other than the current owner can pursue the date in any practical sense. For Seated Liberty half dime specialists building complete date-and-mintmark sets, the 1870-S represents an impossibility that is documented but not achievable. Its place in the series is that of a famous absence, known to exist but permanently out of reach.