Small Butterfly Knife with hooked blade

This Butterfly knife was bought at auction in a lot with other WWII ephemera. I was wondering its origin and if the handles are ivory. I have never seen a hooked blade like this on a Butterfly knife and wondered if anyone has seen a hook like this on a Butterfly knife before The blade is discolored over time i guess. The handle has KRUG & Co and REIMS engraved on it. Couldn't find much about it through searching .
This knife is quite small.
Handles 9cm, Blade is 6½ cm and total length is 15cm