Hi Martin,
You will know already more about your nice rencong as others can add!
Has Kai told you something about the origin? I guess that it is a Gayo rencong, sadly the mouth piece is missing which would be able to pinpoint the origin a little bit better. It's a rare rencong, congrats. What is the handle material? When it is ivory it could be dugong ivory. I personally would polish up the metal parts of the handle.
Attached a pic of some rencong from my collection.
Regards,
Detlef