Respirator, Anti-Gas, Mk. IV, the Mk. IV General Service Respirator, is an Interwar, Second World War and Early Post-War Respirator which has seen use in many different forms all over the world. Starting its life in 1926, and fitted with upgrades to box respirator containers, known as the Type A and Type D Containers, this mask was, at the time, viewed as a leading design by Britain and saw ...