The 2004 United States Mint Silver Proof Set includes 11 uncirculated coins with a composition of all but the $1, nickel, and penny being silver. These coins have a fineness of 0.9 and are struck in proof quality at the San Francisco Mint. Each coin set comes with a Certificate of Authenticity from the U.S. Mint, making it a valuable and collectible item for coin enthusiasts and collectors.