The 1960 U.S. Proof Set with a hard plastic holder is a collectible item produced by the US Mint in the United States. This set includes coins of varying denominations with a proof finish, making it a desirable addition for coin collectors. While the coins are circulated, the set is considered uncirculated due to their pristine proof condition, which adds to its value and appeal to collectors looking for high quality coin sets from the 1960s.