Is this possibly a 1991 D / D ???

[coppersleuth]

Possible evidence of a light second D south ??? It does not appear to me to be mechanical or from "pushed" metal, rather a seemingly legitimate raised ridge.

[Bob P]

The portion outside the mintmark is a 'pushed metal' or plating problem. The line on the bottom of the mintmark looks like a striking problem or a well placed hit. Remember that mintmarks were not hand punched after 1989, so it can not be an RPM. If this were legitimate separation with notching on the mintmark, it would have been considered a doubled die for the date.