The Swiss Schenk B-Maske was a helmet type mask made of green rubber. It featured two round glass eyepieces, an elongated snout, and a cheek-mounted exhale valve. It was for civilian use. This example was made by Schenk around 1930.
Maske = "Mask"
Model stamp under chin "B-1"
Stamps on cheek "M" "B0013"
Metal exhale valve cover
Filter stamps top view "2T 8" "SCHENK"
Filter with plug bottom view
Cardboard box top view "B=1" "Schenk"