Plunkedtt shows dents in his helmet from German gunfire in the trench. Later, the dents are gone.
After the skirmish in the woods, an "unconscious" German prisoner obligingly stands on his feet prior to being carried back to the American lines.
While arguing in the trenches, the Sergeant asks if Plunkett would "be satisfied with the Distinguished Service Cross." This medal for heroism was not awarded until 1918, the year after this scene takes place.
After the fight in camp, one of the 69th soldiers referred to the Alabama boys as "Razorbacks" who are from Arkansas, but a young man from New York could have mixed that up.