Hello, your great grandfather wears Austro Hungarian Army uniform , the cap is that of a officer. He wears also a Karls Bluse , a model of field coat allowed to officers and officials. altough his beard obscured the collar ,on it appears to be either a star or a rosette and behind that a strip of cloth in regimental colour . his coat is without shoulder boards ,another officers feature. he carries a sabre ,not a infantry officer one , its a model for officials. the badges on his cap are unidetifiable. the black armband possibly is the mourning one for the death of Francis Joseph I .weared after November 21th of 1916 ,