Guess no weather sealing means exactly that. Had this out in some rain and looks like I've got some corrosion from it. Never took the lens off are anything, just looked now after about 2 weeks. How would you go about cleaning this? q-tip and isopropyl?
I would tray to carefully use a little soft brush to clean some of the greenish particulates around the shutter plane. The little brown metal dots on the metal surface I would leave unharmed - could be some corrosion, but this wouldn't affect function.