With a normal "soap-and-water" wash of the interior rim of the wheel yielded what is shown in the first picture. 85K miles does NOT wash off.
Using nothing more than a micro fiber cloth, Bar Keepers Friend in the spray bottle (not the abrasive version) and a little elbow grease, yielded what is shown in the 2nd picture...
Did only the fronts while I changed the front brake pads.
I know not many really care about such an obscure place on their car, but don't you agree it looks really, really good?