Mint Proof Set – Unopened Box of 5 Sets (Unsearched). Mint Proof Set commemorates the United States Bicentennial, featuring specially designed reverse sides on the Quarter, Half Dollar, and Dollar coins. Each set includes six coins, all struck at the San Francisco Mint with a mirror-like proof finish. While we strive to ensure the accuracy of our product images and descriptions, please note that the actual item’s appearance may vary slightly.