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"

Similar masks in my collection:  German VM 37, Latvian VEF 39, Dutch Veritex, Swiss SM64, Finnish M39