I am NOT a WWI buff, but that is definitely a WWI Model 1910 hand axe. The M1910 was issued throughout the Interwar years and right through WWII into the Korean conflict. In WWII, the M1910 hand axe had the mfgr's name and date stamped on the head. The surest WWI "tell" on the hand axe itself are the serifs in the "U.S." marking on the head and the handle. That is classic WWI. WWII "U.S." markings, whether stamped or stenciled, were sans serif. The sheath is date stamped, as you suspected. I don't know anything about H&P. In WWII, canvas and duck sheaths, water buckets, tent halves, etc, were supplied separately by canvas mfgrs. I'm not saying it's not the hand axe maker, but, no axe makers with the initials "H&P" are popping out at me, and, it may be the sheath supplier. Nice hand axe. EDIT: Actually, that's better than nice. Everything is in incredible condition for it being 100 years old!
