These old machines, even when new, were not as clean, sterile, and leakproof as what we expect today. That's why there's a drain hole with a jiggling cotterpin to keep it open of dirt!
Unless the front tranny seal and the rear crankshaft "rope seal" are PERFECT, they will mark their territory a bit from time to time.
(IS there such a thing as a "rope seal" that seals perfectly?)
It's your call how much "marking it's territory" you will put up with before tearing it down, and attempting to make it a bit better.
It wouldn't be the first "N" that gets parked over a shallow pan of kitty litter to keep oil drops off of the garage floor (IF it's nearly housebroken and lives inside)!