During the Second World War the British/Canadians employed a number of binocular types with different magnifications for specific applications. A numbering system was used to differentiate each of the specific binocular types. Binoculars were precision optical equipment in which only a few companies had the ability to manufacture so it is not uncommon to find contracts being met by R.E.L. in Canada for the British which would account for the Broad Arrow stamp. The Finnegans marked 1937 Pattern Web case is indeed a British manufactured item as confirmed by the Broad Arrow markings.
I have attached a photographs from my collection of a set of C Broad Arrow stamped American manufactured Bausch & Lomb Optical Co. 8x30 Military Stereo as an example of inter-Allied production of optics.
