Thanks for all the input, guys
Erlikhan is right as to the six pointed star. In my hometown, there are many Turkish people and I never noticed that the star on their flag was five pointed. I examined the piece again and yes... the moon and star were added (soldered ?) to the grip.
I also looked at some books concerning bayonets and the closest thing I could find which had some resemblance to the point of my knife was the blade of a French 1842 sabre-bayonet. It could also be made from the French 1866 sabre-bayonet 'Chassepot' which had a similar blade.
Here are some additional pictures of my piece :
