The 2006 State Quarter Clad Proof Set U.S. Mint Packaging OGP COA is a valuable collection of uncirculated 25 cent coins minted in San Francisco in 2006. Each quarter is made of copper-nickel clad composition and struck as a proof, making them highly sought after by collectors. These coins are certified by the U.S. Mint, ensuring their authenticity and quality. The set includes all 50 states quarters from the year 2006, making it a comprehensive addition to any coin collection.