NBN is listed in The History and Development of the American Guitar by Ken Achard.
Gold-plated early National with custom NBN neck
In a January 1976 Guitar Player cover story article Stephen Stills is holding up this National in the mountain meadow photo, and it is half shown on the other story photo. Here's another (unpublished) photo from the article shoot.
In a June 1979 International Musician and Recording World cover story Stills is playing the National on the cover photo. Here's the cover photo, scanned and cropped. The National is not mentioned in the article. It can be seen but not especially well in a couple of black and white photos in the article.
This resonator can also be seen on the back cover of the Stills album. Here's the album picture, scanned and cropped. Here's the same picture from the back of the Stills album songbook, scanned and cropped. Here's another photo of the National from the songbook.
NBN 5-string long neck banjo
In the January 1976 Guitar Player article Stills lists this banjo (mistakenly listed as N.B.M.). The banjo can be seen on the cover photo.
Bill Danoff is perhaps best known for writing (with his then-wife Taffy Nivert) "I Guess He'd Rather Be in Colorado" and "Take Me Home, Country Roads," both of which were hits for John Denver.
Danoff and Nivert recorded several albums before forming Starland Vocal Band which released "Afternoon Delight" in 1976.
They were responsible for putting together film director Robert Altman and producer Jerry Weintraub for the film Nashville.
Danoff also worked with Emmylou Harris, co-authoring "Boulder to Birmingham" with her.