I almost bought that bass. The guy had it on Craigs List in Florida for over a month and we'd kicked a deal around. Those are great basses but I've been holding out for another '86 TBird II.
I don't think it is a prototype though. I've seen at least four others exactly like it. I think it was a small 2 PUP run by the Gib Custom Shop in 1986-87 after the small TBird II '86 run for Japan.
I'll look thru my photo files. I'm sure I have pics of some of the others like this one.
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OK....found one (below.) I know the guy in LA Guns had one of them. Chip from EnuffZnuff also had one but he swapped out the PUPs to chrome ones and put a Badass bridge on it but you could still see the 3-point studs, plus his was TransCherry. There was another near me on Long Island for sale around 5 years back. There was one in the UK with a headstock repair a few years back...but not sure if it had the top jack...but was an 86-87 Gib Custom Shop one.
But they ARE about as scarce as the 1986 Tbird II ones, so there can't be many.