On August 12, 1974, the three designers were at the Philadelphia Mint, where they ceremonially operated the presses to strike the first coins bearing their designs. These prototypes were exhibited under armed guard at the American Numismatic Association convention in Florida the next day. They differ from all other Bicentennial coins in that they were struck in silver proof without mint mark; other silver proof coins bear an "S" mint mark as struck at the San Francisco Assay Office (as the San Francisco Mint was then known). Coins struck at Denver bear a "D" on the obverse; pieces lacking a mint mark were struck at Philadelphia. Sets of these prototypes were presented to President Gerald Ford, Counselor to the President Anne Armstrong and Director John Warner of the American Revolutionary Bicentennial Administration (the successor to the ARBC). All other first strikes were melted, with copies not even kept for the National Numismatic Collection.