What is this on the reverse of 2003 penny???

Found this last night. It's quite interesting. It appears to be be copper bubbles of some sort. It also appears that a crack runs from the top to the bottom.

 

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looks like a typical dirty penny to me.

 

There are globs of whatever right under United.

 

Looks like dirty nastiness plus plating bubbles to me.

 

@non_cents your the penny guy what do you think? looks to me like pmd

 

It got hot. The zinc started to melt before the copper shell... PMD.

 

technical term?

crud

 

Some sort of PMD. LostDutchman's explanation for the expanded area sounds pretty good.

 

Maybe it came in contact with a corrosive substance. Like an acid.

 

http://chrisfitzgerald.hubpages.com/hub/Separating-Zinc-and-Copper-from-a-Penny