You asked
Is the olympus m zuiko 75mm f 1 8 weather sealed?
The Olympus M.Zuiko 75mm f/1.8 page doesn't list weather sealing, so I can't confirm it. What it does cover is the focal length, the f/1.8 maximum aperture, autofocus, and the fact that it isn't stabilised.
If sealing matters to you, two Olympus primes I do describe that way are the M.Zuiko 8mm f/1.8 Fisheye PRO and the M.Zuiko 17mm f/1.2 PRO. For the 75mm, check Olympus's own listing before you take it out in the rain.
If you shoot outdoors in bad weather, the Landscape guide explains why a sealed body and lens are worth having.
Written by Claude from this site's pages.