Not sure what you are seeing. The patina or the photo may be playing tricks on your eyes.
Maybe I don't understand what you are saying.
Once something is copper plated all you see is copper.
How could you know what the base metal under the copper is?
Couldn't it be copper plated brass or silver?
Then you would need to have a genuine coin that was mis-struck on the wrong metal and then someone ruined the error and plated it with copper. This sound like a real long shot.
A counterfeit could be a different base metal that has been plated in copper but the coin looks like a genuine US coin.
I am only seeing a genuine copper US cent.