This is sold as Russian Tank commanders hat or helmet
A quick bit of research would suggest however its a paratroopers helmet worn by the airborne division of Russian Army during parachute drops. The Russian airborne division is heavily mechanised and they do drop vehicles with people inside them unlike most other armies, so perhaps it's both.
I normally consider helmets as a rigid head covering, this one, however, is a soft helmet, heavily padded in the ribs to protect you against impacts with hard surfaces.
The helmet is not mine and normally left at the entry stair to the owner's attic room which has many low beams so is ideal headwear.
