John, I really think the only way to authenticate is through a TPG....maybe somebody like biokemist would know whether a partial plating is possible. Seems unlikely, but I'm not familiar with the process and think a guess would do you no good at all.
Yes, it is possible to have a partially plated cent. However, I do not think this is one. A similar effect can be produced by heating a Zincoln on a hotplate, it will take on a dark silvery appearance with some darker brown "rusty" areas- that would be cuprous oxide.
No, heating on a hotplate would not roughen the coin. Zinc has a bright bluish-white color, not the darker grey like the color of this cent. The "rust" I was referring to completely covers the periphery of the coin. That is also the part of the coin in primary contact with the hotplate so the rims and periphery would undergo the heaviest oxidation.