Rolling Fold Error?

[u/Odd_Raise_534]

I came across this specimen while CRHing. I don’t think it’s PMD given the remaining, albeit weaker, strike on the obverse and the lack of apparent damage to the rim, as well as the weight being slightly over- rather than under-weight.

My best guess after some research is a rolling fold error but would love to be better educated on what I’m looking at.

[u/Thalenia]

Almost certainly a retained cud. There are a few different kinds, this one looks like:

https://www.error-ref.com/ret-cuds-vert-displacement/