It was a Croatian battalion from Zagreb. It was deployed in two brigades of the 25th division (49th and 50th) until 1917. The division fought in the 2nd Army in Galicia. For a while in 1917 it belonged directly subordinated to the XV corps on the Italian front. Then the battalion got a job as a hinterland control unit. In 1918, the battalion returned to the Italian front.
The Kappenazeichen shown in this post is the unit’s more common insignia. There was also an enamel version that was larger than this, partly decorated with the Croatian red and white checkerboard motif. It is interesting that the badge was presented on the postcard with a green background. I have never seen such a green badge, maybe it was just a design plan.