Not sure if perhaps another planchet got in the way of this one from the laser-plater. Notice the build up of copper around it. (I am thinking this is the most likely reason). Or maybe was this struck after plating which stripped it? But it looks too clean for that to have happened. Or was the planchet flawed before plating or striking? A combination of some of these? I already know it is genuine, so no need to speculate if it was altered. But any educated opinions as to why it looks this way on the REVERSE would be much appreciated, and greetings from Buffalo, NY. Here is the obverse as well.
Nice partial plating error - Since no one has witnessed the copper-plating operation of these Copper Coated Zinc planchets (which is done outside the Mint, by the outside supplier), I can't tell you exactly why it has that pattern on the reverse, but I've seen similar patterns on them. In general, it's because the copper plating didn't completely cover the planchet (obviously); why, in that pattern (and obv. too), I can't explain. Something prevented the copper plating from adhering to the unstuck planchet. Nice error, and in my opinion, these (both partial and 100% unplated cents) are much scarcer than collectors realize.
It's zinc, and in my opinion, if you DON'T do something to it that you otherwise wouldn't do to a coin, yes, it will deteriorate quite badly. Like what? Oh, maybe a light coating of a very clean expensive machine oil. I know it's a long obsolete product and virtually nobody has any of it any more, but my bottle of Eastman Kodak's Light Machine Oil used by old projector repairmen would come into play eventually if that coin were mine. It was rumored to be actual whale oil.
I was not aware that cent planchets were plated using a laser-enhanced electroplating process. Can you please explain how it's done?