The face piece is made of thick rubber colored either white or black. The eye pieces are made of the same "unbreakable" glass as the later T.35. The mask sports the standard Italian five straps system. At the bottom of the face piece stands the intake-outtake piece, which houses the exhale valve and the connection to the hose. At the end of the hose stands the M.33 filter, attached with tape.
The mask came in a two-sections satchel, one for the mask and the other for the filter and hose. The filter section had a sloped metal piece to allow airflow to the filter's bottom. The mask also came with anti-fogging lenses and soap.
The Autoprotettore S.C.M. 37 was a self-contained breathing apparatus made by Spasciani. This kind of device was used by people who needed a continuous flow of oxygen, for example, firefighters. The face piece was connected through a hose to the backpack, which was not very large.
During the Spanish Civil War there were no officially exported gas masks, hence no type designation and no service regulations or instructions. The Italian troops fighting there sported a black colored T.35 or an M.33 (or M.31) with a GM-30 intake-outtake piece with either a Spanish or a German filter and satchel.
Some of those masks were also issued to local Spanish groups.