Sorry for the delay. I just saw this. One of the more commonly encountered regimental shoulder straps, the "Grenadier-Regt. König Friedrich III. (2.Schlesisches) Nr. 11" strap is a M1915 pattern, originally meant for the Bluse, but also seen as pattern upgrade on earlier model tunics. This regiment saw action against the American forces in the Meuse-Argonne offensive, at which time they had an estimated losses of 3,200 men, two thirds of which were prisoners.
Chip