Dom --
It's kind of hard for me to tell from the pics, but I've drawn (to the best of my ability) what the cross section of the "ballock" knife looks like. The genoui I post as comparison (which I do think is a bayonet blade) has a more typical three-sided triangular cross section. I'm not sure this qualifies, since the third "side" of the triangle seems more like two convex sides, if I am making myself clear.
Anyway if it is a lebel that could certainly narrow the origins!
Thanks,
--Radleigh