It reads “AM LOT 1089-37B” “37MM GUN” “MODEL OF 1916″ 1836-31-WPS Co”. Here is the info that I found about the round.
“The M1916 37mm gun was developed by the French and used primarily by French and American forces in WWI for destroying machine gun emplacements. It was fairly good at this under fluid, mobile conditions, but inferior to mortars for static trench warfare. It was still in limited service by World War II, but generally relegated to training and use as a sub-caliber addition for larger guns.
Ammunition was of two types initially, a 1-pound solid steel shell and a high explosive round. The solid round was found to be largely ineffective, and replaced with a bursting shell of cast iron and filled with black powder. Mounting for the gun was either a fixed tripod or wheeled carriage.
Mechanically, the M1916 used a rotating breechblock and hydraulic recoil absorber coupled with a spring recuperator. In addition to use as an infantry gun, the M1916 was also mounted in the early US M1917 Renault tank.”
(info used written by Forgotten Weapons- at Forgotten Weapons Website-Model 1916 More info on this weapon and others can be found at Forgotten Weapons Website
Here is the weapon as it stood with troops in WWI