Precision Altimeters

[Ka-2b Pilot]

https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/960x544/precision_altimeters_c03fa3c0c83fa888ac710da3dc2175f0e928ded 7.jpg
Personally I would have called these high altitude barometers as they only read pressure from 100-300mb.
They were reportedly fitted to a Valiant, possibly XD818, but what would they have been used for?
I was asked this question on Facebook after posting images of Varsity instruments and radio boxes.
I have never seen them before.

[jimjim1]

Google search of images for [precision altimeter] returns a couple of quite similar hits. One very similar.
https://www.worthpoint.com/worthopedia/negretti-zambra-precision-altimeter-1778306776
Negretti Zambra precision altimeter

I guess it might say "Negretti & Zambra" under those Stbd and Port labels.

Here is a facebook page by an ex-employee.

https://www.facebook.com/people/Negretti-Zambra-Aviation-Ltd/100057295096589/
"the great firm I joined in 1979 aged 16. NZ is now part of Meggitt"

There are images of your "Port" device.
https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/502x302/negrett_zambra_facebook_26cc32600e2e11a8a17ed91d21a83f09af1b 5b14.png



https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/1440x1080/negretti_zambra_precision_altimeter_360_f3d78a7e8ad5c1c6e9b3 17477aa50961_17595399bf75d7c76de624d1fa7fceeb3aad215c.jpg

https://hydrography.pro/presta17/altimeter/63-paulin-system-precision-altimeter.html
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/800x800/paulin_system_precision_altimeter_7cf6b7e2aac5dddcf33196fe57 4893bcb4092668.jpg

https://vavasseur-antiques.com/portfolios/precision-altimeter-negretti-zambra-p-157780/
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/2000x1333/negretti_zambra_precision_barometer_p157780_13a_8a25c7f80bf9 27088446c98e7dd9ea582e13b8e3.jpg