Stop in for a cup of coffee

Hey Hops the one rear would not turn over so I opened it up and there was moisture and crap in there. It has an S on the top of the case. And it looks like it may be but I don't know. I asked Max about it and he said he never had it open and he got it out of a junk yard. I am sure he told me he got it out of an old car that he junked. Can they be cleaned up? I didn't see much rust on the ring gear but it was like rusty sawdust in there.