Looks like elongated plating blisters and the rim is from a slightly misaligned die when it was minted/stamped/pressed - whatever y'all call it these days!
I have the "feel" of them as delamination of the copper cladding, in conjunction with some bubbling underneath, understandable when the protective surface is cracked and therefore allowing the zinc to react all the more quickly.
USER=73174]@Markus1959[/USER] Not feisty - thankful! I just learned something here! Made me look up what the "NEW TO ME" definition of that characteristic that the error guys have on the web. I learned something different decades ago - that it's the slight spread found next to the clip that is virtually always present rather than "flatness" opposite the clip which is often not there. Seems silly to me to have a name for something that is missing much of the time. Apparently, the young'uns are standardizing/studying errors more closely and setting things straight for us old guys. Also, plating blisters may eventually erupt causing a lamination. That is just one reason (my Post#9) laminations occur.
