I have a faceless penny no stamp on back are face
One use for a copper slug is that collectors of elongated coins like to use them instead of hunting down and cleaning pre 1982 pennies.
This is what's known as a slug. They're used for vending machines and they're illegal. Usually they are something larger and more worthwhile - like a quarter, which makes more sense. I don't know why anyone would bother to make a slug of a penny.
I have a penny that is print on one side and nothing on the other