The 1968-S ''No S'' Proof Dime
"When contemplating some of the most intriguing Modern US coins, several of the No S Proof coins come in mind. In particular, the 1968-S Proof Dime -- the first date for the Roosevelt Dime Proofs without the "S" mint mark. After thorough research, experts concluded that the "S" mint mark was not punched into the die creating this new variety. The mistake must have been caught by mint employees early in the process as only a few examples managed to escape. This was also the first date for any series of US coins where the "S" mint mark was omitted."
The 1968-S ''No S'' Proof Dime 
