All good to know stuff. I was hesitant when he mentioned polishing it up, hence I haven't done anything to it so far. I did some reading before posting here and some other sites and knew about never cleaning the tang, since apparently its super critical in ID'ing and dating a blade.
I also don't think he has any interest in selling it ever. If he is really insistent on polishing it then I'll probably do it for him, since honestly at least if I do it, it won't be a dremel job. But knowing its potentially valuable I'll encourage leaving it.
It did have a scabbard, its at the top of my first picture, with the silver stripes and electrical tape, all full of gouges from something sharp. I guess he did that when he was a kid. It holds the sword, but otherwise is a lost cause.
Last thing, Ray, are you saying that the tang translates to Seki ju Kunihiro, or is that an opinion based on the appearance?
Thx