2012 United States Mint Proof Set - 14 pc set. Key Set, Low Mintage. The 2012-S Proof Set comes in three cases. One case contains the Cent, Nickel, Dime, Half Dollar, and Native American Dollar; one contains the five America the Beautiful Quarters, while the third case houses the four Presidential Dollars. The coins are inserted into holes in a cardboard holder, and then sealed inside a two-piece, clear plastic case. The cases and certificate of authenticity were inserted into a brown and black card-stock box.