Last time I took my 1911 out shooting I just put it back in the safe after I was done. Never cleaned it or anything. This was probably a month ago. I took it out of the safe today, and noticed this on the slide... I don't know for sure that it's rust, but I tried getting it off with a cloth and I just got a little bit of brown gunk on the cloth, that looks strikingly similar to rust. What's the best way to get rid of this? It's a cheap no name slide my grandfather got at a gun show a while back and gave to me, but I would still like to clean it up rather than buy a whole new slide. Thanks!