So Help Please! Is This Some Error Or Cleaning (2007 Cent)

There are many examples of zinc cents suffering from solid-state diffusion on ebay. I notice that in some, plating blisters extend from the copper areas into the zinc-colored areas. This would be impossible in an incomplete plating error.

All interesting suggestions, CoinHi. Methinks we have the makings of another column. Gotta do some more research though, and hopefully get some examples under my microscope.

@mikediamond ... PLEASE don't put those into circulation ... they'll end up on ebay as " $10,000 valuable errors I've never seen before..."

Mike, I would be glad to send you 20 of the better ones. I pulled them out again I have 2 rolls of them in various stages. My thought on them is that they didn't get completely plated. The center plating ended up being too thin, then when they were struck the thin plating fell off.

Here's an instructive example of solid-state diffusion. https://www.ebay.com/itm/375275381314. On the obverse, you can see that the plating irregularities seen in the normal copper plating continue unbroken into the zinc-colored area. This would be impossible in a case of incomplete plating and equally impossible in a case of plating that has flaked off after the strike. I'm now rather partial to CoinHi's hypothesis, that the heat generated by the strike, perhaps combined with unusually thin plating, leads zinc atoms to penetrate the copper plating or for copper atoms to sink down into the underlying zinc. I'll have to read more on solid-state diffusion to see which direction of migration is more likely.

This may constitute confirmatory evidence of solid-state diffusion. However, it's also possible that the copper plating has simply darkened/blackened over time. You see this sometimes in die caps, where the working face gradually changes over the years from a copper color to a dark gray or black color. I also don't like the look of this cent, as it appears to have a slightly rough surface texture on both its struck and unstruck portions. Perhaps it was subjected to some mild sandblasting, which exposed the zinc on the struck tab. I find it to be an ambiguous specimen.

In this case, it's hard for me to determine which gray areas represent zinc that was exposed at the moment of the strike versus areas that changed color and darkened well after the strike. I suspect it's a mixture of both.

Thanks Mike.