1990 United States Proof Set, 5 Coins Inside!!. Proof Set sales dipped slightly again in 1990, even though the issue price remained at $11.00, making this set a little tougher to find.Each set contained five coins: One example each of the Lincoln Cent, Jefferson Nickel, Roosevelt Dime (Copper-Nickel Clad), Washington Quarter (Copper-Nickel Clad), and Kennedy Half Dollar (Copper-Nickel Clad).About the sets: All coins in the 1990-S Proof Set were intended to have a Cameo or Deep Cameo Finish.Some 1990-S Proof Sets contain Cents that lack the “S” mintmark. These are mistakes that were made when the Philadelphia Mint (responsible for producing the dies for the San Francisco Mint) failed to add the mintmark to a Proof obverse die. Approximately 3,500 “S-Less” Cents were produced, with an unknown quantity going into the Prestige Sets of this year.