bubbly coin? perhaps from the champagne region? I don't think that it's a lamination. I've seen others like it, and it does appear to have trapped air inside! does it float?
It might be a piece out of the die. If it is, it will rob metal from the area directly opposite of the blob---faded letters no letters, or maybe an indent in the field.
It's aluminum and 17.2mm in diameter, so I think it may. It's not my coin. It's somebody I know who has it. I'll ask.
I see this kind of damage often with worn aluminum coins. I suspect it has been exposed to heat damage and thus parts of it bulged out.
^ agreed. I've seen this type of bubbling often on coins that had been soldered or exposed to other forms of high heat.
