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I wondered if they looked different.
All the SKF bearings I have laying around within arm's reach have markings etched on the edge of the outer race on one side only, so you'd only be able to see them once installed in a hub if the mechanic puts them in with the markings to the outside. I'm not suggesting for one moment that there are people obsessive enough to actually do that as a matter of course...
..you get the idea..