Gibson only built 718 Thunderbird IIs between 1963 and the 1965 discontinuation date due to a lawsuit by Fender, which insanely claimed the Thunderbird looked too much like their Precision bass (one of the great WTF moments in guitar history).
I've heard this may be at least partially urban legend. Maybe a cease and desist? Also, I believe it was to do with the offset Jazz Bass body. Funny thing is, the later non-rev is more Fender-ish than the original!
Glenn started modifying this bass soon after he bought it. This photo shows a Guild pickup in place of the original Gibson and the pick guard has been removed. This is the only color photo of this bass that I have found so far. I've been in touch with Drew Cornick who offered to try and locate a few more photos of this bass for reference in the restoration of mine.I feel it's rather important from a documentation standpoint to mention that the sides of the fretboard appear to be unpainted. Many Gibson experts, including some friends who have original NR Thunderbirds, state that Gibson always painted the sides of the fretboards on custom color basses. Knowing how Gibson did things it seems entirely possible they painted some fretboard sides and left some unpainted.
I want it, hahaha!