Vintage World War I U.S. Army Canteen - also could be a very early Boy Scout Canteen!  This canteen still has the original screw-type metal cap with the rubber seal and chain.  It appears to be made of aluminum and is about 7.5" in diameter.  Please see condition description and pics.  

Thanks for looking!  Please visit my store for more vintage military memorabilia, Scouting collectibles, and other great items!