Ariel is, I fear, absolutely correct in his observations.
I would suggest you enjoy it as it is, except for mild oiling or waxing to reduce further degradation. It does appear to have genuine age and this speaks as to its history.
Several years ago, I found an omi-no-yari
at Brimfield. I was second in line as there was a 'proper' nihonto collector already looking at it. He asked the dealer the price and then observed in response that, from losses to the engravings, it was already a bit too tired from repeated polishings. I paused and allowed him to take six steps away and then I immediately repeated the mentioned price back to the generalist dealer and promptly peeled this requested price from my bankroll. We were both smiling. For me this was a 'Brimfield eureka!'
I was prepared to enjoy it as it was and still am. Some wax on the blade and a tiny touch of glue here and there, but otherwise still exactly as it was. I am not saying that the nihonto collecting community is wrong in their quest for flawless perfection, only that, characterizing myself as a general ethnographic arms collector, this is not my goal - for me the excitement is in the tangible evidence of very different times and places that such pieces provide.
It has already been presented
in these forums, so I'll not repeat the rest. There is a link to the Nihonto Message Board in that thread.