Not in, but on the coin just like your spots but they were more black in 2009. I refer to them as water spots. Someday I'll pop one on the SEM-EDXFR instrument and determine the composition but for now, I think they are likely mineralized, insoluble salts of some sort. In my trials, they cannot be removed without damaging the surfaces.
What are these freckles on a cent called? I love the look of them; I thought they were PMD from heat when I first noticed one.
@BadThad and @robec - Thanks for the great info and pics regarding the gas bubbles. I had not heard of this before and really started to wonder after I realized I had seen numerous examples of these in circulation from around the same late 1980's dates. The above pics are all of the same 1987 D Lincoln. Found this one in a roll from bank just in the last month or so.
Hmm I guess I figured those gas bubble coins were coins that had a condition problem, like corrosion, so I always toss them back. They're not pretty.
Got the camera out, not opening my AirTites though, so not optimal pics. Deep red patina with tons of luster: