These were all Proof coins and folks need to know the difference. The Bottom line is that SIX copper nickel IKEs carry the S Mint Mark. Even if the Silver coin grades out at MS69. In 1973, at least three S Mint coins were struck on copper-nickel clad planchets and if someone has a 'blue pack' coin that they suspect is I can say is that it would have considerably more value than the it's Silver counterpart.
