Just to follow this up since you’ve all been great in contributing to the hunt.. The DH-106 would definitely be a strong possibility, the history of the unit is that it’s one of my late grandfather’s keepsakes along the years and there are some pieces we never had a chance to talk on! He did work on the DH-106 but I can’t recall or find any history or intersections of work where a VC-10 would have been in frame but it’s still very possible he was hands on with one at some point.. The Vickers Vanguard VC-9 is possible but I notice that’s reportedly half the fuel load of these gauges and unsure on number of tanks?

As Oracal says it’s possible it’s not a VC-10 and that Smiths just used similar design language and/or parts for these refuelling panels, not unlikely given that something like this must have been some of the first of their kind to be produced and it wasn’t yet any kind of a mass or mature type of a unit?

I will reach out to some DeHavilland experts in the meantime and see if maybe it can be confirmed!