From what I've gathered from other, more knowledgeable members, that looks like "zinc rot". Modern pennies are a thin coating of copper over a zinc core. Zinc rot occurs when during the original striking of the coin, a small, even minute, fracture of the copper plating occurs and allows moisture/water to come in contact with the zinc core. Zinc is reactive to water. Over time, the zinc and moisture combination begins to "rot" and eventually you have what you see here. This interaction is more common around the mint mark.
Thank you, I'm trying to learn and your time and information you guys provide is VERY much appreciated
Very informative link. It also has plating blisters and has photos that look like that other post " #1 ". Thanks. That link has gone into my " Coin Tools " folder.
