1990 Lincoln Cent

Yes, as john1 said. Gas bubbles trapped below the copper plating. Quite common and worth face value, but I'd keep it as a good example of such.

Yes, not too common, maybe one out of 20,000? minted show this in my experience. Unfortunately, its just common enough to not be worth much, which believe me is the curse of many of my finds- ha ha.

Still, I think your coin shows a great example of this problem and that many collectors would "enjoy" learning about the gas bubble problem by looking at your coin.

FAR more common than 1:20,000 on all years 1982-1991. More like 1:50, and some BU rolls are ALL pimply. They ahd major problems with this at the mint that didn't get resolved (more or less) until 1992.

My own opinion is that these definitely detrimentally affect the value of the coin, the grade, and everything else. They are not errors, they are a nuisance. If I found a 1983 DDR or a 1984 DDO with this sort of bubbling on it, I would shed a tear and toss it in the reject pile for the bank...really. No serious die variety collector wants a valuable die variety with this problem on it.

I would not toss either of those back myself. Quite the opposite - I would go out and celebrate! I guess we all have different standards:).

Worth what is marked on the reverse. Spend it before it becomes a copper Hershey's kiss wrapper.