1975 United States Mint Proof Set, 5 Coins Inside!. Original packaging: The individual coins of the 1975-S Proof Set were sealed in a two-piece, clear plastic case. Raised rings of plastic separated the coins from each other, and a red, felt-covered paper insert was added for visual impact. The clear plastic case containing the coins was inserted into a molded, black plastic frame with the raised silver letters "UNITED STATES PROOF SET", and a hinged flap that could be flipped over for display purposes. A black card cover imprinted with silver letters, "United States Proof Set • 1975" protected both the case and the frame.