So I'm reading an article about 'penny hoarders'.
It mentiones that they want pre-1982 pennies because they are 95% copper and worth a lot more than a penny.
So the guy in the article had this to say:
"The copper has such a different sound than zinc pennies do," Henry said. "Real money has that definite sound of money and if you listen to a modern zinc penny, they don't sound the same, they sound sort of tinny."