I thought I'd wait to post until you had gotten all the good advice and then give you mine
I bought one of these rare Nippon Kogaku 6.5 CM scopes in 2010. Certainly a quite sought after telescope. I did a lot of "soughting" after that first purchase and now have...uh... 5. Hardly rare in my house but in the bigger picture probably. They appear on eBay once or twice a year. Sometimes without the mount and tripod.
My best condition/complete telescope and kit is # 2978. It is the exact kit as yours with the 6 eyepieces. The export tag is dated Nov. 14, 1956. I paid by far the most for that scope. Not understanding how reserve bidding works I put in my worst case scenario bid on eBay. I think the auction had a few days to run and was at like $500. To prepare for the inevitable snipe I typed in $2000 and "ding ding ding" I met the reserve which meant even if no-one bid against me I was in for 2K! And no one bid against me Oh and then there was the shipping costs! My other less complete kits came in for about $1000 each through Craigslist postings. I'm sure they are worth less as I'm always willing to pay too much for things I really want.
That first Nippon Kogaku 6.5 was acquired through an eBay auction. I picked it up in WA. It had been stored at a work site. The work site was a gravel crushing/concrete production plant. The lens, well, I couldn't see anything resembling glass when I looked in. The first views were full of diffusion as the light scattered through the "dust" coat. I posted asking for advice just as you did here on CN. A most prominent member at the time and fearless Nippon Kogaku afficianado Clint Caveman Whitman offered to clean the glass for me. He did a fantastic job.
You are smart to be asking questions and considering using the telescope as is. As others have said there are risks inherent in removing the lens elements. None of my Nippon Kogaku telescopes exhibit centered "Newton's Rings" indicating that the foil spacers are uneven in thickness. Maybe the optics would be better if the lens elements were separated and new foil was installed but I've chipped too much glass over the last 50+ years to do that myself. I'm sorta fine working with Unitron, Swift, Royal Astro glass but not Nippon Kogaku nor Goto Kogaku, nor Takahashi. Some folks here are fearless and steady handed, I'm not.
To that end I have sent a few lenses to Barry at D&G Optical. There was a time when he would clean and re-spacer and even collimate if you sent him the whole optical tube for a very reasonable price. I'm not sure if that is a service he now performs. D&G is in PA.
I have had a few lenses where the coating had gone south on the crown or sky side element. I soaked them in warm sulfuric acid for a few days and the rest of the coating dissolved leaving a clear lens. These were Swift lenses. Easy to remove from the metal cell unlike Nippon Kogaku. Don't do this to the flint (eyepiece side) element as they are different glass types and the acid will harm the glass, I've read.
So my advice. Use the telescope as is. Treasure it as it has family history. If you think the views are being impacted by spurious light consider having the glass cleaned if you can find a lab or fearless individual here. If you do it yourself be very careful and good luck to you.
The Nippon Kogaku .965 eyepieces are very fine. The 7mm and 9mm Orthoscopics are divine. The 18mm H and 25mm H are exquisite. The 5mm O offers too much magnification for my seeing conditions. The 12.5 H is a good eyepiece as well but such a tiny hole to look through!
I have wiped down the legs of these telescopes with Murphy's Oil Soap and they respond well. Others here have their favorite waxes and cleaners.
I see Samhain ended. Time to let the bonfire die down and start observing again. Looks safe out here... Good night.