 Copper prices began to rise in 1973 , to such an extent that the intrinsic value of the coin approached a cent , and citizens began to hoard cents , hoping to realize a profit . The Mint decided to switch to an aluminum cent . Over a million and a half such pieces were struck in the second half of 1973 , though they were dated 1974 . At congressional hearings , representatives of the vending machine industry testified that aluminum cents would jam their equipment , and the Mint backed away from its proposal . Mint director Mary Brooks sought the return of samples which had been distributed to members of Congress , but 14 remained missing , with the recipients affecting not to know what had become of them . One aluminum cent was donated to the Smithsonian Institution for the National Numismatic Collection ; another was reportedly found by a US Capitol Police Officer . 
