Many of the UK tracks, for example "Rendezvous 6:02" and "In The Dead Of The Night" sound like Jazz Bass. Live photos show him favouring the Precision 'though he switched for a black Ibanez RS 900 ("The Phil Lynott bass") for the last dates.
King Crimson headquarters
www.dgmlive.com once had some rehearsal tapes from Robert Fripp's "Exposure" sessions available (Fripp, Wetton and Phil Collins) and those tracks sounded like a Jazz Bass too. Ditto for the 1978 released Jack-Knife album "I Wish You Would".
Wetton had the Jazz Bass already back in 1974:
I wonder if he ever used it then?