Heres a picture of a 1989 D, im not sure if it is a D over D. The first two pictures show the thick D while the second shows a normal mintmark.
Hi Austin, No it isn't a RPM. It appears to be the exposure of the inner zinc layer due to the very thin copper layer on the surface being ruptured. Some times mild machine doubling damage can cause it. I think some call it "zinc creep", but I am not sure on that With the super bowl, not as many on today. Jim
A normal 89-D with the start of zinc rot, semm them a million times! A normal 89-D with the start of zinc rot, semm them a million times!