Actually, there is. That is a 1911, not a 1911A1, as evidenced by the long trigger, the absence of relief cuts in the frame behind the trigger, and the straight mainspring housing.
I trust your expertise but could it also have been issued during WW2 as well?
I'm sure if they had them in 1918 they were still good for the second world war.
Unless they retired the 1911 and only gave brand new 1911A1 to the troops.