I know that the possibility of an RPM on a state quarter can't happen. How would this occur is it machine doubling?
Yes, RPM cannot occur as the MintMark are no longer manually stamped. RPMs were due to a person stamping the MM by hand and not exactly getting a 2nd or 3rd strike, etc completely in the right spot. So with that out of the possibility .. what are the other options ? FYI .. I think you'll end up doing yourself a disservice over time with such a high magnification to search for errors.
I'm pretty sure that there are only three forms of doubling on a mintmark that can occur since 1990: 1) true doubled die 2) machine doubling 3) die deterioration doubling. Someone please correct me if I'm wrong.
since 1990 Mintmarks are no longer hand punched on any denomination and are part of the hub/working die. If it's any coin dated after 1990 it's a safe bet that whatever it is, it's NOT an RPM, and usually it's going to be mechanical/die deterioration doubling.
