So, he was a Feldwebel in one of "german" infantry regiments of AH. Assuming that the regiment was garrisoned in Lemberg according to the data from 1914 it can be regiment number 15, 30, 55, 80 or 95.
Comparing colors, I believe that 15, 55 or 95 are too dark, so either 15 or 80.
Infanterieregiment Freiherr von Georgi Nr.15
Infanterieregiment Wilhelm Ernst Grossherzog von Sachsen-Weimar-Eisenach, Herzog zu Sachsen Nr.80