Which metals could be inside the copper-clad pennies minted after 1983?

Pennies minted in the United States cents from mid-1982 to the present are copper-plated with zinc inside. By weight, the zinc core comprises 97.5% of the coins' metal.

There were some 2009 bicentennial cents minted specifically for collectors that were made from 95 percent copper and 5 percent tin and zinc,