Someone who is most likely to know is Alan Jackson, as he played in a band with Jet and knew him very well.
This amp is indeed a rarity, our bass player in The Four Blades had the stock one with the normal split front and the only other one I remember seeing belonged to a terrific guitarist from Leeds, Richard Harding, who played a lot of Chet Atkins stuff in his group The Cresters.
I'm particularly interested in the speaker cloth, as it is the later Vox black background rather than the brown that is familiar with the early sixties. Vox didn't' make many of these and especially after about 1967/8, so I would be interested in the true origins of this combo. It doesn't make any sense to me to have a full cloth front on a combo, that look was normally reserved for extension speaker cabinets (check out the later Beatles amps), so I smell a rat and would suggest this is a home made DIY effort and someone is telling porkies.