Your pictures shows a Mk XIIIC altimeter, 6A/446. Ref 6A/445 if you want a luminous version.
My references show that the 6A/437 is a luminous Mk XIIID. The Mk XIIID is a 40000 feet altimeter where as the Mk XIIIC is a 30000 feet altimeter.

Thanks, you are quite correct. The new photo definitely shows 0-40,000′ although I think a Stirling would struggle to make 20k:rolleyes:

6A/437 is definitely what we’re after

cheers

John