I have a number of coins with those kinds of uneven lumps on them too. I have one where a raised line goes almost straight across one side of the whole coin, all the way from side to side, and it has the same look as these kinds of "gas bubbles" under the plating.
I think I'm starting to recognize the difference between gas bubble types bumps, and die chips, when I see them now. Maybe I'm learning at last?
PS: I see a lot of these kinds of bumps and raised lines starting from 1997? I think it is, when they changed from the 12 sided one cents to round again.
When I searched my box of 2010 pennies, I found countless coins with these types of bubbles. I am becoming more like Dottir. I also have had so many that I can now pretty well tell between a bubble and a dot.
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