US M17 A2 Gas Mask Large MSA w/ Nylon Carry Bag & Accessories 1984. Mask shows some scuffs over, lens show some scuffs & scratches, the elastic head harness has lost some of its elasticity and shows some dirt and the inlet valve is dented in slightly (See Picture #21) but this is still in good overall condition. A Large M17 gas mask is a Medium that has a large nose piece (See Picture #3). A large gas mask has the M above the forehead with a white marked’L’ added to it. Because the mask is used, the L is only lightly stamped. The Manual and the chemical paper show rusty staples. Please see all 24 Pics.