The SzR2-50 but mostly known as SR-1 mask is a Polish gas mask (licensed ShR-1) designed and produced in the Cold War for soldiers with head wounds (like the Soviet ShR-2). It was most likely issued to medics and field hospitals.
The facepiece is very similar to the typical Soviet rubber hood masks (ShM-41) and to the that time standard Polish military issued SzM-41M. The mask has a thicker rubber hood with a thinner neck part and a "pillow" to fix the neck in case of a spine injury. On the back of the mask there are 3 pairs of straps to provide airtight seal. The eyepieces are normal crimped on and a Tissot tube system provides defogging which is not integrated.
EO-14 canister filter would connected by a hose.
The kits commonly came with a light green bag similar to that of the MUA kit, it contains four pockets. One is for the mask, another for the hose, and the last large one is for the filter. The last pocket is either for a decontamination kit or medical supplies.