Perma Fin's lack of surface buildup, which keeps it from filling and obscuring stampings and engravings, also prevents it from hiding flaws such as scratches and rust pits. This rifle had a few rusty spots on its barrel, and you can still find them because Perma Fin doesn't fill and build on a surface as paint does.
I took no pains to remove rust pits, but you could do so with care. It's tough to do it right, though, because you can easily end up with a part that's out-of-round or asymmetrical. Sometimes, refinished rust pits look better than the aftermath of an attempt to remove them.
I was slightly concerned about reassembly, because I figured I'd be sure to knock a couple parts together and scratch them up. I got along pretty well, though - Perma Fin is pretty tough stuff.