I have the same marks on a rear here at the house. Came from a Max Wedge Car when the pinion broke. The pinion backed into the sure grip and re-machined it! Haven't run it yet, but I don't see any problems with running it.
Yeas ago I used to rebuild 8 3/4 rears. That mark IS from a pinion bearing failure (or the nut got loose) where the pinion got into the case. Probably didn't do the pinion any good (If it hasn't been replaced) but the case is ok to run.