Large calibre case maker's mark M.A.C. (Possibly Canadian)

I have a few WW1 era artillery cases with the marker’s mark “M.A.C.” and Canadian property marks (/|\ inside C).

Does anyone know who used this maker’s mark?

Canadian collectors, can you help me here?

Thanks in advance for any info.

M.A.C. is the Montreal Ammunition Company, Montreal.

Regards
TonyE