Although a relatively unknown brand of equipment, Nikko seems to be an underdog of the era based on several other comments I've read on Audiokarma. I could hardly find any information on this unit, but I picked it up anyway because the price was right—zero dollars.
The guy giving it away said it was broken, and had it stored on his garage floor with a flimsy door swinging open and closed. It was in a very sad state. The wooden cabinet was covered in grime and splattered with paint, the glass in the faceplate was missing, its feet were missing, and there was dirt and debris covering the whole thing—presumably due to the open garage door? It's really quite amazing the amount of abuse these 1970s receivers can take. I always kick myself for not taking "before" photos. I really should have in this case.
When I got it home, sure enough, it was dead. I was hoping all it needed was a new fuse so I opened it up and found a surprise. It didn't use fuses at all, rather breaker swiches. I flipped all of the breakers back on and tried again. It lit up, well, only partially. Most of the bulbs were burned out.
I went to work giving it a good scrub, ordered new bulbs from dgwojo.com, bought new feet from the hardware store, and had new glass cut for the faceplate (a mother with her own picture framing business helps here). The work speaks for itself—even though I didn't do anything particularly technical in regards to the restoration, I am kinda proud of how it turned out.
The only permanent damage is a scratch on the tuner area, where you can see blue light glowing through. I thought maybe using an opaque silver sharpie to color it in would work at masking it, but I'm afraid to try in case it ends up horribly ugly. It's actually less noticible in person.