I'm by no way a Barber dime expert, but on the reverse to the left of the O and D sure does look like somebody tried to "erase", and then the way the crud is inside the M looks to me like somebody tried cleaning and just couldn't get that area cleaned out. I'd be interested myself to hear what some of the real experts on Barber dimes have to say about those areas on the reverse.
I'm with a mid to high AU grade as well. Looks like a small amount of rub plus the dirt in Liberty and on the reverse of M suggests it has seen some circulation. I would guess that it is somewhere in the $80 range. I wouldn't hesitate busting it out for a type set or album if I had to, but that is just my opinion.