Good day Pierre,
Can't give you details on ALL the markings. However, the "circle with waves" is an American mark I believe (actually a flaming grenade). I think it is for the American Ordnance Corps. Along with the "C Broad Arrow" (arrow within the letter C) indicates equipment used by Canadian forces.
Other, more experienced collectors might be able to give you more detail, but I would think that the Smith & Wesson pistol in question was part of a war purchase from the US to Canada
Hope this gives you some help.