Yep, #26. When you put the new one on, lube the rubber lip and watch to make sure it climbs up on the smooth area of the shaft without rolling.

John is right about the bushing, if it is worn the shaft won't sit in the center of the seal, causing it to fail. Chances are though that the old seal has either gotten chewed up by years of dirt, or stiff from age. It might even be a leather seal if it is old enough.