The Provost T1 that I helped to rebuild in 1979 had altimeters 6A 3380 (new ref – 4333298).

Using your logic, I suppose 50k rules out the Trident as well?:D:D

Well, the trident isn’t completely ruled out. I work a lot with pressure guages, and I am led to believe these are most accurate at mid scale, so on this logic a trident may qualify. But as not being an ex RAF aircraft, this does discount it a bit. The company I used to work for had a fair bit of avionics from Trident G-ARPP which was scrapped in Glasgow, hence the hesitation in identification. The altimeter was stored away from the Trident avionics.

Cheers
Scotty