I've been saving copper pennies for years. In 1982, they were mixed, so a non-destructive way to tell is weigh them: Zn pennies are 2.5 g and Cu pennies about 3.1 g I've also been saving all my nickels, which are 75% Ni & 25% Cu. Today, a copper penny has almost $0.04 of copper and nickels are wor...