Split plating. It wasn't uncommon in the 80s to have the copper split along the mm. This exposes the zinc core, and over time, the zinc will start to corrode. The bubbly appearance is an indication that the zinc is corroding under the surface (similar to rust bubbling under the paint on a car fender)
RPM's fall in the Variety Category different from a mint error. But that is not a RPM. This is what eventually happen to your Cent -