[gp]

enclosed the pictures of the bichaq from Croatia and 2 from Bosnia with similar decoration, so you can compare.
when I look at the grip / hilt of what the owner calls "sword", I would not call it a yataghan, but looks more like the long bichaqs of 40 cm

as for the grip/handle / hilt: the types for the bichaqs were derived from the several types yataghans in the Ottoman empire and found on the Balkans; from Makedonia, Bulgaria, parts of what is now known as Greece ( as the Greek world was way bigger than the present state!) through Albania, Serbia, Bosnia, Dalmatia and parts of Croatia...numbers 14 and 18 come close to the above "sword"

I would recommend cleaning the metal of the knife and scabbard either with some colorless olive oil and the leather as well or with some other leather prerserving material ( like for ancient saddle and saddle bags) to stop further deterioration and restore it a little to its former beauty