It looks copper to me, plus some circulation light toning. If the reverse copper plating had been removed, you'd see the zinc planchet itself. It's just toning. Not an error coin, imo.
I believe your Cent was urinated on. That rainbow colored toning is what occurs when that is done to it. Always wash your hands very well when handling all coins.
I agree, toning. I don't know why people keep thinking there are errors with these cents unless their like this .
I do like his image of the edge though, It clearly shows the beveling from the edge to the rim seen on coins that aren't fully struck. The better the strike the wider the flat part on the edge and the smaller the bevels.
Someone finally found my toilet test subject! That's my "T" identifying mark in the right obverse field.
