From 1965-1969 all half dollars were at least 40% silver. Wheat cents were beginning to disappear from change. Whenever anything quits being common they begin to be hoarded and start being sold. The current iteration are the bulk lots of cents on ebay guaranteed to be copper pre-1982 with no zincolns. When wheat cents were 2 cents each and steel cents were three cents loose cents were run down conveyor belts under powerful electro magnets and steel cents disappeared from circulation almost overnight.