I guess its a Steyr-Mannlicher M1895/35. It was designed by Ferdinand Ritter von Mannlicher and used a refined version of his revolutionary straight-pull action (causing the Landser-nickname "Ruck-Zuck" for this rifle).
It was initially adopted and employed by the Austro-Hungarian army throughout World War I, and retained post-war by both the Austrian and Hungarian armies. The main foreign user was Bulgaria, which, starting in 1903, acquired large numbers and continued using them throughout both world wars. Numbers of these rifles also saw use in World War II, particularly by second line, reservist, and partizan units in Romania, Yugoslavia, Italy and to lesser degree, Germany ("Volkssturm").