Sighting Scope WW1/WW2

[things_green]

another query for the great collective knowledge here....

Would this scope have been utilised with a specific artillery piece or is a generic unit used on various pieces or a tripod?

Made in 1917 by the London based 'Periscopic Prism Co. Ltd'
Nomenclature; 'Variable Power Telescope No2'

then come WW2 all that was struck-out and it was reclassified
'Telescope Sighting No. 38 MkII'
(I wonder if was the buggers at BB Ltd that took away the variable power option?)

30 1/2" long x 2 1/2" dia at the lens cap.
It had 3 magnification options x7, x14, x21 (although it appears to be locked on the x21)

I really have to firmly ID some of this kit and rehome it before I join the Dead Parrot fraternity!

Brent. NZ