Origin of this dagger?

[Sajen]

Hello,

just get a mail from my friend. He think that it is dugong or very old and worn hippo ivory. When you can see in the cracks black dots in a line it is hippo ivory. He say the look from up on the handle speak for dugong.
But he is like I am nearly sure that it isn't bone.

Like said before, it is difficult to give a save opinion by pictures only.

Regards,

Detlef