M 33  S.A.B. Spasciani Autoprottetori  Military oxygen breathing apparatus mask (1933 ).
Same mask facepiece as the common M 31 / M 33 mask but with an inside half mask and corrugated hose directly fitted on the mask.

 

M-31 / M 33 Military gas mask ( 1931 / 1933 ).
The M-31 has been the sucessor of the leder M-29 mask and of the M 31 Penna Respiratore designed for the Italian Army.

First of a long serie of masks designed on a simple flat shape moulding principle of the facepiece