The 1964 US Silver Proof Set in original envelope is a valuable collection of uncirculated 50 cent silver coins minted in Philadelphia by the U.S. Mint. This set includes coins with a fineness of 0.9, struck in proof quality, making them highly sought after by collectors. The coins are in pristine condition and come with original certification from the U.S. Mint, adding to their authenticity and value as a piece of American numismatic history.