Gas Mask! (56k warning)

In my basement [Full of lots of ww2 crap and patented inventions] I found a gas mask [I'm assuming from ww2] but I'm not totally sure if it is from ww2 or if it's even American mask [it does say US on it, but then I noticed a third s..]. I was wondering if someone could possibly identify it.

Pictures: I took pictures from the front, both sides, and inside. I also took a shot of me wearing it [At this age, it's the reverse of what a gas mask should be, it's got some rather odd smells, though I cleaned it out as best I could] !ill x)

and now for the blurry as hell inside..