Here is my Springfield Armory US Army 1911 .45ACP pistol serial number 107382 made in 1914. Closeups show "S" marking for Springfield Armory on slide lock and thumb safety and "S P" on barrel lug.
Springfield pistols use a distinctive magazine (made at Springfield) with folded over and brazed bottom lips as well as a copper plated section at the rear top of the walls and a lanyard loop on the floor plate. The magazine also has a distinctive coloring due to the brazing and heat treatment. A few Springfield magazines have been found without lanyard loops, however it is uncertain if these were ever issued with any pistol.
According to Poyer's Model 1911 book the same "Type 4" front sights were used on Springfield Armory 1911s made 1914-1917. The sight was integral to the slide and milled from the steel ingot from which the slide was cut.