Hey guys. I bought a canteen cup from my local surplus/camp store. I know they are made in aluminum and stainless steel and was wondering how to tell which mine is. they said it was stainless but im not sure if they actually knew or not. it was ten bucks which seems about where the stainless ones are in price but that place has been known to be a bit pricey. it says us 91 pac fab on it. any help??? thanks guys.