@Alexandru Moldoveanu Yes to Linear Plating Bubble It's a Copper Plated Zinc Cent. Plating bubbles are common on them.
For some unknown (to me) reason, these are especially common on 1984-1986 cents. They seem to have fixed it mostly by 1987. A version of it even appears on some 1984-1986 proof cents, and they are double plated planchets. Bottom line: zinc is a horrible coining metal in general.
Yup, proof cent planchets are produced in a segregated batch and receive twice the copper plating, to prevent strike-through of the zinc. Oh, except in 2009, when they weren't Zincolns at all.
Sometimes it's hard to tell where the acetone ends and my fingers begin. I got a box of blue nitrile gloves, but my hand looks the same color. Seriously, though, I did pick up a Stone Mountain half as an "extra" coin in a two-coin lot, and it looked kind of hazy-schmazy. After an acetone bath, it's the better of my two Stone Mountain halves. The luster booms. This is why I do auctions - sometimes you score nicely.
