That's because we are all stumped!
I really like this knife.
So seeing as I know folk often don't want to be the first to throw out some ideas.
I guess it better be me!
The first thing that occured was the similarity to Spanish knives.
But the hilt and pommel shape make me think that the spanish 'feel' is a red herring and this is more likely to be African. Have a look at this Yoruba knife:
http://www.vikingsword.com/vb/showthread.php?t=13369