Opinion please--Gunto w/Old blade?

[trenchwarfare]

Don't do anything to the nakago. That rust, is considered patina on Japanese blades. It tells you the true age of the sword. Yours has some deep pitting. The nakago should be black, not gray. It has been cleaned. The only thing that is sometimes done, is to burnish the tang, with a piece of bone. This will only remove surface rust scale, so as to be able to read the signature.