I found a Kennedy half with an odd bubble on the obverse. I have no clue how this could have occurred. The reverse shows no damage. I don't think it is a CUD? Any help is appreciated.
I think Kennedy needs some iodine. Ya don't see qoiters like THAT, nowadays.
No clue, as you say the back is unaffected, other than, possibly a micro piece of trash blew in during the melding process, and whatever impurity is in there, has corroded and/or attempted to come to the surface.
I also considered a contaminant inside the planchet but the guy at the LCS thought an expansion like that would cause a surface crack. Doesn't mean he is right, just his opinion. There are no cracks and no reciprocating bulge on the reverse. It's just baffling. And if there is a containment wouldn't that be a mint error as it was most likely present in the planchet?
I had the same thoughts as the above when I saw the pic of the reverse...Heat. It bubbled between layers, maybe from a little air pocket that expanded when it got hot.