This here has meanwhile arrived as well
and like Dave said, Mr Giffin built a mighty fine bass. Whether is was ever a legitimate Gibson product, I have my doubts (one of the tuners has "Hamer" on it, though it is otherwise identical with the other three which read "Gibson", don't think they do that at Gibson Custom Shops, do they?) though things like the volute etc are typical of Gibson.
While I have yet to restring it with rounds (it features flats and while these sound good on it, I just don't think that an Explorer with flats is right!), I'm impressed by how the two close proximity Model Gs sound. The neck one full, but not unfocused, the bridge one barky, but with ample bass. Both of them together though cancels out too much of the mids for my taste and leaves you with an aquired taste scooped sound.
The neck. THAT neck. Think of earliest P Bass halved baseball bats. Supposedly this short scale neck is to have come from a 1978 Triumph, but my (earlier) Triumph has a much thinner neck and no volute. It is also made of maho, while this here seems to be maple from the look of it. A fat maple neck for a Triumph?
Body is allegedly from a mid-80ies regular Explorer which could be the case judging from the shape, but then it must be one of the early alder body ones, not the later maho bodies. And of course it features a stripey maple top.
Sound of the stubby necked one is surprisingly vintage and fat, great E string for a short scale. I'm expecting the Model Gs to come alive a bit more with fresh rounds.
Uwe