I'm sure you'll get lots of feedback on this, but I'll give it a shot.
The large diameter surface all the way in is the surface the inner bearing seal rides on. It does not rotate, and is machined as part of the spindle. The smaller o.d. sleeve appears to me to be a portion of the wheel bearing, from the pic it looks like the tapered part of the wheel bearing that contacts spindle surface itself. It looks to me like it may have seized to the spindle when the bearing failed....