Definitely plated - or rather part plated. I would have said so even without the copper streak, but that proves it.
We used to do this with the old pre-decimal pennies using Silver Nitrate if we could get it, or other metal salts if not. Can be very convincing.
BTW:

We used to do this with the old pre-decimal pennies using Silver Nitrate if we could get it, or other metal salts if not. Can be very convincing.
BTW:























