Gresham's law
With the passage of the Coinage Act of 1965, the dime's silver content was removed. Dimes from 1965 to the present are struck from a clad metal composed of outer layers of 75% copper and 25% nickel alloy, bonded to a pure copper core. Pre-1965 dimes have followed Gresham's law and vanished from ordinary currency circulation at face value. Most now trade as informal bullion coins known as junk silver, priced at some multiple of face value, which price follows the spot price of silver on commodity markets.