Oil Seals

Is it possible that my outer front wheel bearing retainer oil seal and my inner universal differential outer seal are the same. I measured the bore size several times and it comes up the same at 2.882. My paperwork tells me they are the same inside and outside demensions and the part number is Garlock 3900 or the CR 28824 seal. I know for a fact I do not have the smaller outside seal whos demension is 2.875. So far I have not found a way to acurately measure the brake drum seal size because of the tight area. My micrometers wont fit in the drum area when its open enough to measure the hub seal size.
The more I know the less I know..