The material is canvas or burlap (?) like, with a metal respirator in the front. My grandfather, who is now deceased, worked for a company that did a lot of top secret work for the government back in the day, and he may have been given this as a "precaution". This was found in his basement, and I never got a chance to ask him about it.

Does anyone know how much this would be worth, or how I can get more info on this? Any war buffs and/or military antique buffs out there?

Thanks!
I live in Canada.