The Austrian M-34 Leder B-Maske was made of leather, and had two large oval plastic eyepieces.  It was used for both military and industrial purposes.  This example has a specialized exhale valve located on left cheek for use by telephone operators.  It was made by Drager Wien in 1934 and is missing its filter and head straps.
Leder = "Leather"

 

Similar masks in my collection:  German Leder B-Maske, German ASM