I wish I'd said something about that way up top of the thread (sorry), but I really don't know how much difference it'll make. (If I just glance at a thread, sometimes I don't really see everything.) You said it was a used compressor; did you pull it yourself at a junkyard, or one of those places where it's already taken off the car?

Was oil sorta pouring out as you handled the compressor? If not, then maybe you're OK.