Absolutely no doubt but that it is a S&W Military & Police (later known as the Model 10.)
Canada was a big buyer of these and the full history is detailed in my book "Canadian Military Handguns, 1855-1985"
"In 1932, the British Army adopted a lighter top-break revolver - the Enfield No.2 Mk I - chambered for the new .380/200 service cartridge (a military loading of the .38 Smith & Wesson employing a somewhat heavier 200 grain bullet). During the 1930's, the fledgling RCAF obtained 585 of these British pistols, but with the outbreak of WWII, Canada elected to adopt the Smith & Wesson "Military & Police" model revolver (in effect, a lighter version of the "Hand Ejector") which, in .38S&W chambering, would accommodate the standard .380/200 British service cartridge. Over 118,000 of these revolvers were purchased from 1939 through 1943.
Configuration of Canadian-issue arms: Double-action revolver, ranged from early acquisitions with commercial polished blue finish and checkered walnut grips through brushed blue to later "wartime finishes" of sandblast blue and sandblast parkerizing with smooth wood grips; 4", 5" and 6" barrels (5" most common); .38 caliber; 6-round capacity; cylinder swings out to the left for loading and extraction. In service, 1939-1964."
From
www.Canadiansoldiers.com, based on my book.