I found this coin a few years ago. I saved it since I thought it was unusual, but I'm wondering what exactly it is? It's got a small bump on it. It may be hard to see in the pictures but it's big enough to easily feel it when i touch it.
I will say it's not an occluded gas bubble. Those usually occur in solid Planchets such as the old Copper Planchet Cents. I will say the Cupronickel clad received some extreme heat and caused a small blister. Post mint damage. Not a mint error of any kind unfortunately.