Major2,
Not intending to blow your mind … but:
a) another terminology "correction": strictly speaking, a holster was actually referred to in British/Commonwealth military terminology as a "pistol case" …
b) the standard-issue pistol of the Canadian military during WWII was actually the Smith & Wesson Military & Police Model revolver, chambered for the .38 S&W cartridge (and thus for the .British .380 Service Revolver cartridge which was a military version of the .38 S&W.) Canada acquired in excess of 118,000 such S&W revolvers, and only about 3,500 of the standard UK-issue .380 No. 2 Enfield revolver (starting in 1937, for issue to the Royal Canadian Air Force) but there were
no official Canadian acquisitions of .380 Webley revolvers (which were only secondary military issue in the UK …

Mind you, lots of Canadian-made web equipment was sent to help equip the UK forces … so your Canadian-made pistol case is actually quite suitable for your Webley …
As you presumably know, like many military carriage systems, P'37 Web Equipment consisted of various component pieces which could be assembled in a variety of ways.
Once my vision returns to some semblance of order following the cataract surgery I've recently undergone, and I then get some new glasses so I can actually see clearly again and can locate things without so much squinting and peering, I should be able to provide you with a PDF file of the complete original Pattern 1937 Web Equipment Manual I have, if you wish. (Can't seem to lay my hands on it right now. It is a 1940 Canadian reprinting of the British 1939 manual.)
In the meantime, here are a few images from it that I have in a file on my computer …
Firstly, the cover page and Figure 9 illustrating the "Set for Officers, Certain W.Os. and N.C.Os." being worn -

The relevant pages itemizing the various standard "sets" of P37 equipment, with highlighting for the sets which incorporated a pistol case/holster -

Figure 8, showing the "Set for Officers, Certain W.Os. and N.C.Os." laid out, assembled, (back of waistbelt facing up) -

Figures 10 and 11, "Set for Personnel Armed With Pistol Only" -


Figure 20, showing the early "Pistol Case with Cartridge Loops" - otherwise termed the "Pistol Case, Royal Armoured Corps" - being worn -

I don't seem to have a scan of Figure 21 saved … which I presume is a similar "assembled layout seen from the back", like the others above.
As you might surmise, this was the early version of the pistol case with cartridge loops you posted a photo of, above. The theory was that the extreme drop of the holster (which was strapped to the leg) would minimize hangups of the holstered pistol for personnel exiting confined armoured vehicle hatches … but the low-slung position was not all that convenient … and the pistol could still get hung up on the edge of the hatch … but then it was way down there on the leg, making it even more difficult to clear the hangup. Not long into the war, the design was altered to the much shorter drop style you show, with the leg strap eliminated … and most of the original long ones got altered to the much shorter type … with the result that unaltered long ones are relatively rare.
My collection of P'37 Equipment includes an unissued Canadian-made version of the long style -
