The official United States Mint Presidential $1 Coin Proof Set™ contains the four new Presidential $1 Coins. Proof coins are extraordinarily brilliant with sharp relief and a mirror-like background. Their frosted, sculpted foregrounds give them a special “cameo” effect, created by the exacting proofing process. Proof blanks are specially cleaned, polished and treated to ensure high-quality strikes. The blanks are then fed into presses fitted with hand-polished dies and struck at least twice to ensure sharp, high relief.