&####127464;&####127462; Canadian Respirator, Anti-Gas, Mk. IV T-Mic dated August 1943 by Dominion Rubber Company Lot 542 size small. The Canadian Production Mk. IV General Service Respirator being an exact copy of the British Mk. IV alongside the Canadian copy of the Mk. V GSR and the Respirator Anti-Gas Light series as a means to modernize the Canadian Armed Forces Equipment. An officer in the Canadian Armed Forces, Major G. Morrison, thought of the idea of simply importing British Respirators to Canada to improve Canadian Anti-Gas equipment as most of what they were using at the time were Small Box Respirators, though this idea was shut down as Canada had a much greater interest in producing their own equipment. After much trial and error they finally were able to secure the plans to produce Mk. IV GSR masks via the Safety Supply Company in 1932 to work together in the production of said masks. The kit for the Canadian Mk.