U.S. Army XM28E4 Riot Control Agent Mask
The U.S. Army XM28E4 Riot Control Agent Mask was designed for use by soldiers deploying tear gas in the Vietcong tunnels during the Vietnam War. Its internal cheek filters and low profile made it extremely light and compact. This example was made by Mine Safety Appliances in 1968.
Similar masks in my collection: U.S. CD V-805