Italian Maschera Antigas I.A.C. M.31

The Italian Maschera Antigas I.A.C. M.31 was made of smooth dark brown rubber. This example features a speech diaphragm/exhale valve incorporated into the hose, and was made by Industria Articoli Caoutchouc around 1933.
Maschera Antigas = "Gas Mask"
Industria Articoli Caoutchouc = "Rubber Articles Industry"
Similar masks in my collection: Belgian M1931, Belgian M1934, Italian S.A.B. M33, Spanish M33