What would cause a quarter to bubble?

[creskol]

I found this in a bubble wrap envelope in the parking lot at the post office today.
Before I turn it in on Monday, I am curious as to what would make the bubble ..front and back on this coin.
It is really much nicer than the photo shows it, and I imagine somebody bought it for its unique properties.

 

[reale bill]

most likely was in a house fire.

 

[duggap]

I agree that was one hot quarter. Just about to the melting point.

 

[BosnMate]

Only thing that could do it would be heat. Probably has a lot to do with being clad, because silver would just melt without making a bubble. I've often wondered if the zinclons would burn. They use zinc in rocket fuel, but I've never put a torch to a penny. I'm going to have to try that, but I'll procrastinate, so if anyone else is interested, try it and report back.

 

[bradyboy]

IM confused but could be wrong
first, looks like it was hit with a small torch
BUT
the heating / torching of this coin dosent seem to match up, face and back side
Maybe im wrong
Brady

 

[Gunrunner61]

Not a clue! But I have one with a bubble too, Although mine is much smaller about the size of the "o" on my keyboard, I too have wondered what created it................HH