Mint Solid Silver Proof Liberty & Britannia Medal. With Box & CoA. An iconic silver medal, the result of the Royal Mint of England and the U. Creating a first ever collaboration piece. Only 32,904 pieces minted, and this. Piece is NO LONGER AVAILABLE from the mint! Uncirculated, and ungraded, but with certification from the Philadelphia Mint. Proof finish, Mint Mark’P’. Composition 99.9% silver.