[mapsjanhere]

In regards to value, from the pictures you showed it's not in particularly great condition. While it has a Ferlach proof mark, it does have no Ferlach maker's mark (and as Ferlach was the center of Austrian gun making, every Ferlach maker would have marked it clearly). So you have a nice stalking rifle of unknown Austrian manufacture, most likely in an obsolete caliber if the 8.9 mark indicates it (you should make a chamber cast), made between the wars and "liberated" by some GI after the war. Typically they are advertised (but not sold) for a $1,000 - $1,500 on gunbroker.
If I see it at a gun show with a $750 price I might take a close look at it for the craftsmanship, but not more. BTW in German these guns are known as Ischl Stutzen, after the Austrian Emporer Franz Joseph's favorite vacation (and hunting) town.