$500 is a good deal, it looks like the damage is from something previous, unless it has been sitting exposed for a while and thats why it rusted, but even then it wouldnt really rust like that unless it had all the oil cleaned off of it, it is an auburn type unit, yes it has c-clip eliminators, yes 4.10 gear, but i dont think auburn makes axles??? maybe moser, strange, ford motorsport or superior axles......