Just A Damaged Mintmark, Or Maybe An RPM On This 1979 S? Susan B Anthony Dollar

After finding that wide rim, been paying a lil more attentionto the SBA's, where very little had been put down on the SBA. This one's MM caught my eye, as the 1st angle looked like a D, then S, now I mostly say its an S. Lat Late last night think I saw a B and an A, but I was unable to find any RPM's listed for any SBA's, I think maybe 1 DDR, if memory serves! Now I get the '79 has been around long enough for any varieties or errors to have already been discovered, but I guess that kinda leads to a 2nd question, whats average time for the many,trained, collectors to figure out how many diff die varieties after a new years start hitting the streets? I mean, dont I see where older, we'll say 60"s, 70' & '80's still having discoveries? anyways all that bs to ask yall what yall think sbout this MM