I thought I saw a couple forging lines in 2 of the pictures, but that blade is beat up, and without a window you can not know what is under that rust and tarnish on the damn thing. The nakago looks like it is covered in firescale or slime, though I am sure it isn't. Bob Benson among others Would be able to open an inch or 2 up for you. I think Louis Skeebo is on the board and he may be able to help.
If you choose not to get a window:
This is not my suggestion to anyone just a possible cleaning method that can work on a dieing and decaying sword, so don't hang me. I in no way endorse doing anything non traditional to a blade, just offering a way to stop the blade from rotting more:
You could take a mild soap and water and washcloth and clean the blade. Then Dry it completely. then take some windex to it to lift any residue and crap, then wd-40 the hell out of it to penetrate down past the top rust. then have it wrapped it in soft cloths completely soaked it in wd-40 for 24 hours, respraye and flip it for another 24 hours, then take a clean wd 40 cloth and wipe the blade down gently and alot of old crud should come off. After words you may be able to see alot more of the blade.
My suggestion is to let someone more knowledgable see it and window it if you want to keep it. But you have to stop that rust, and I know that wrapping it in oil soaked cloths has been mentioned on this site before as a remedy.