The current composition of pennies is 97.5% zinc and 2.5% copper. They were changed over in 1982 ( a split year) from 95% copper, 5% zinc. People would be unhappy if they were sold .999 or .9999 copper bars and they got 5% zinc. Most coin shops have a machine to test the purity of their wares, due to counterfeiting. While I've never looked for a bar of melted pre 82 pennies, I'm sure they exist. They would just need to be stamped as such and people would buy them. You'd be surprised what's out there in bar form. Lead, bismuth, antimony, all sorts of stuff. It's all stamped for purity, tho. All privately minted bullion has the purity marks on the round, like government backed bullion does. All I'm pointing out is people want to know what they're buying. They want to trust in the retailers. I believe in England, say you were melting and pouring silver, each piece has to be assayed (taken to a government licensed shop tested and stamped) to be sold. (Not 100% sure on how the English laws work, look it up if you're curious.) Btw, if you don't have a pure silver round or coin, go to the local coin shop and ask to hold an American Silver Eagle. Not only are they beautiful coins, they're the standard the rest of the world lives up to when minting bullion. Beware, they've got a hefty premium on them, lol