Well, that's the second one I have seen now, and I am equally as intrigued as the first time, when GJer
@Odes posted one a few years ago, linked
here.
The interesting aspect for me, as a Billings & Spencer guy, is that these wrenches are
dead ringers for the B&S "Duo-Forged" M- series wrenches that B&S made during WWII, as I noted on his thread.
That tells me that in the 1940's B&S still had some kind of corporate association with the conglomeration of their Canadian branch with the two other companies that became Canada Foundries and Forgings in 1912, as the article you linked states. Maybe they even used them to produce wrenches.
Either way, it appears that Canada Forge made their own wrenches with the exact same pattern as the B&S "Duo-Forged" M-series wrenches. Same dies except the markings. Possibly (and perhaps we can say probably) at the same time. That "C-5-4" could very well be a date code on those, either May 1944 or April 1945. Note that
@Odes' was a C-6-4.