Russian Aviators Face Mask

We were advised when purchased this mask was used by airmen in exposed crew positions to insulate the face and prevent frostbite and that it dates from circa WWII. We would not profess to be experts on Soviet era flying kit so we will leave it to prospective purchasers to ascertain exactly what we have here. We have however been able to match the mask very closely with a Russian example in an aviation museum so the facts look to be correct. It does not carry a makers label to give any clues although on the elastic straps are two ink stamps but these are not very clear but we can make out a '40' that might indicate a manufacturing date of 1940? The mask itself is in excellent condition and made from soft tan leather with the inside being lined with short hair fur as found on a small rodent. So if you are into Russian flight clothing (or S & M! this one could be for you!