The rare 1984 $1 coin was struck on a 10-cent blank in error, instead of a $1 blank, meaning the coin is silver rather than gold. One of the coins went to auction with a price guide of between $2,000 ...

Although it was never a coin intended for circulation, the 1971-S Eisenhower dollar prototype is one of the most valuable silver dollars ... A planchet is a coin blank that's the size and metal ...