2020-S United States Mint Silver Proof Set. This premium 10-coin set features coins struck at the San Francisco Mint in stunning proof quality with a. 999 fine silver composition for the quarters, half-dollar, and dime. Original Government Packaging (OGP): The coins are protectively housed in their original US Mint display lenses. Certificate of Authenticity (COA): Includes the official mint documentation verifying the set’s specifications.