for alternatives. >> paul montgomery tells me the story. he's a rare-coin dealer and author. and he explains that the mint's solution is to switch from costly copper to a cheaper metal. what was the composition of them? >> the coin is made out of 96 percent aluminum. >> the mint's proud of the coin. it strikes a million and a half and even hands out a few to members of congress before its release. but the aluminum penny is a bigger '70s flop than the gremlin or the leisure suit. >> the coins didn't work in vending machines, uh, i guess because of the metal. kids would swallow 'em, and they wouldn't show up in x-rays, either. >> so instead of circulating the coins, the mint melts them down. and it takes back the few it handed out. the 1974 aluminum penny becomes as elusive as the proverbial unicorn... or maybe not. >> i began doing additional research, which led me to think