US coins

The penny started production in 1793. It was made with 100% copper when first made, but is now only copper plated with mainly zinc. In 1943, due to resource shortages from WWII, it was made tin-plated steel, but changed to brass the next year.

The nickel started production in 1866, and it is made of 75% copper and 25% nickel.

The dime started production in 1768, and it was made out of 90% sliver and 10% copper. It has now been changed to 90% copper and 10% nickel.

The quarter started production in 1796. It was made of 90% silver, but now is made of 90% copper and 10% nickel.

Lets change, say, the quarter, to it's original composition.
Just the silver in it is worth $3 already.

So that is some research on coins.