One of the issues with a lens like this is the lack of other known examples!
If there was a known batch of lenses with this finish, collectors would know about them and look for them. This is the only one I have seen or heard of---in the era it was produced---the finish looks like a good match to a Nikon F2 titan but none have been seen offered with those cameras.
My gut feelings say it's geniune Nikon, but there are no documents or provance provided that would make that totaly clear.
This may have been special ordered by a PJ, Nikon is known for doing stuff like that.
Now, regarding selling this piece, I would try www.Nikonians.org