<P> The first known proposal for a decimal - based coinage system in the United States was made in 1783 by Thomas Jefferson, Benjamin Franklin, Alexander Hamilton, and David Rittenhouse . Hamilton, the nation's first Secretary of the Treasury, recommended the issuance of six such coins in 1791, in a report to Congress . Among the six was a silver coin, "which shall be, in weight and value, one tenth part of a silver unit or dollar". </P> <P> From 1796 to 1837, dimes were composed of 89.24 percent silver and 10.76 percent copper, the value of which required the coins to be physically very small to prevent their intrinsic value being worth more than face value . Thus dimes are made small and thin . The silver percentage was increased to 90.0 percent with the introduction of the Seated Liberty dime; the use of a richer alloy was offset by reducing the diameter from 18.8 millimeters (0.740 inch) to its current figure of 17.9 millimeters (0.705 inch). </P> <P> With the passage of the Coinage Act of 1965, the dime's silver content was removed . Dimes from 1965 to the present are composed of outer layers of 75 percent copper and 25 percent nickel, bonded to a pure copper core . Starting in 1992, the U.S. Mint began issuing Silver Proof Sets annually, which contain dimes composed of the pre-1965 standard of 90 percent silver and 10 percent copper . These sets are intended solely for collectors, and are not meant for general circulation . </P> <P> Since its introduction in 1796, the dime has been issued in six different major types, excluding the 1792 "disme". The name for each type (except for the Barber dime) indicates the design on the coin's obverse . </P>

When was the last year dimes were made of silver