Have you weight it yet? How much does it weight? It look like plated to me or some high school experimental science project.
Nice pics! I'd be inclined to call that an unplated planchet. Can you get a few pics of the edge? There will be others around soon to give you a better idea of what you have.
Please don't hold coins with metal tweezers! You WILL do damage to them. 3 grams is high. Does your scale weigh out to two decimal points? Your coin should weigh 2.5 grams (+/- 0.10 gram) and just a little less than that with no plating. I see no evidence of your coin ever having its copper plate. That's my opinion, but I may be wrong. There will be others here soon with more info. If it is unplated, it's a great find.
I would assume it is zinc plated. This is quite an easy thing to do- my friends and I used to do this for school demonstrations. After plating, you can heat the cents and they will turn bright gold colored as the zinc alloys with the copper to form brass. Yours looks old. We usually preferred to do it on shiny cents as the zinc plating would give a shiny surface. Not sure how you can tell if it’s a legit error but I can tell you when I finished with the cents, i dumped them into my change bowl so they eventually went back into circulation.
I would say either plated or someone has done a very good job of removing the copper plating. A non-plated cent should have smooth surfaces and show cartwheel luster. On this coin the surfaces are rough and there is no cartwheel.
There are three possibilities 1. Unplated planchet - this would be struck full-on by the dies and would be sharp and clear and would weigh 2.5g 2. Plated struck coin - nickel, chrome, zinc over the copper plating. It would have a little mushy appearance as the overplating doesn't quite follow the details as evenly. Weight around 2.5g (you can't measure the weight of a few microns of plating with any scale outside of lab grade equipment). 3. Acid stripped. Would weigh around 2.5g (stripping off a couple of microns of copper plating isn't measurable either). Will leave a rough finish and likely some copper in the nooks and cranies. as the acid doesn't get everywhere evenly. #3 is most likely
Quite a nice analysis. I will read other sites to fully understand your observations. The coin is smooth and doesn't feel rough, or look rough to me though. This would be post mint then? Thanks Burton.
It has had enough wear/abrasion that it is worn through the copper plating on the high areas exposing the zinc.
I see just enough on the surface to make me think that coin has had that thin copper layer stripped away.