The 1968 No S Proof Dime is a modern rarity and one of the most dramatic errors the Mint has ever made. The "error" in this case is that the Mint left the mintmark off the die when it was prepared in Philadelphia before shipment to San Francisco. This has turned out to be one of the rarest of the "No S" Proof coins, exceeded only by the 1975 No S Dime (of which only two are known). Since its inception in 1986, PCGS has certified only 18 1968 No S Proof Dimes, 12 of which are brilliant Proofs and 6 of which are Cameo Proofss. As of July 2011, the finest examples certified by PCGS include five PR68s and 3 PR68CAMs.