Coinage Act of 1965
The Coinage Act of 1965 (4 years after Reagan's 'Encroaching Control' speech) removed the silver from American dimes and quarters and reduced the amount of silver in half-dollars (half-dollars would be removed after a few years).
Speech Relevance
From Encroaching Control:
Lenin said the way to destroy capitalism is to debauch the currency. Through a quiet process of planned inflation, a government can quietly and unobservedly confiscate the wealth of its citizens. Henry VIII did it openly. He substituted copper for silver in the coinage of the day.
From approx. 1542 to 1551, Henry VIII did substitute copper for silver in the coinage of the day. As noted above, in 1965, the United States did the same thing, shifting from a composition of 90% silver and 10% copper to one with two layers of a 75% copper, 25% nickel mix covering a 100% copper core. This change was made in the dime, quarter and half-dollar coins.