Anthony dollar's value is a clear example of that. This odd gold-toned coin happened when the planchet (or coin blank) for a Sacagawea dollar was fed into the coin press with the dies for the 1999 ...

Most Peace silver dollars were placed directly into circulation, Atlanta Gold & Coin Buyers noted ... led to there not being enough silver in the blank to completely fill the highest point ...

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 ...