Again, I wish to thank everyone. A very knowledgeable gentleman, with impeccable background (a PHD ) was kind enough to take the time and give me an evaluation. I will leave his name out, out of respect of privacy, unless he chooses otherwise. I called his association- turns out he is also a member here. I owe many thanks to him, certainly. His evaluation, so very well written, follows....
“ Okay, Chris, looking at the photos from the link, you have what's called a wakizashi, which is a Japanese blade between 12"-24" long on the hacho, the cutting edge. The sugata, or overall shape looks to be Kanbun-Shinto, which is mid-1600s. Looking at the nakago, the mekugiana, or hole, has been drilled, rather than chiseled, which, again, puts the time of its manufacture after 1600.
From the amount of rust on the blade, I doubt that more photos will tell me very much, to be honest. I just checked on the mei & see that you've already contacted the Nihonto Message Board, where I'm a member. The Mutsu-no-kami Yoshiyuki signature can be seen at ( https://nihontoclub.com/smiths/YOS1044),& there might be some history around the blade IF the signature is valid.
The problem is, quite simply, that the blade would first need to be professionally polished, at around $100/inch. Then it would need a new habaki that fits in the blade in front of the nakago, which adds about $350, plus a new shirasaya, or wooden storage case, $400, So, now the wakizashi is prepared, you would send it off to Japan to the NBTHK shinsa, which would authenticate the blade, adding several hundred dollars for the agent to handle the blade's transfer, plus anywhere from $100-$350 for the authentication. Then you would know if your blade was really made by Yoshiyuki...& the blade would probably have a market value of about $1200, depending on whether there are any major flaws that show up during polishing.
Supposedly, a blade made by that smith was used by a famous Japanese statesman, Sakamoto Ryoma, during a fight that killed him, but the actual blade is in a Kyoto museum. So, my professional opinion is to just put some penetrating oil on the blade, & let it soak with a towel wrapped around it. Some of the rust should come off, so it will look cleaner, but you'll never get a clean-looking blade without having it polished, & it just doesn't look like it's worth the money.”
Again, I am so appreciative.