It is a balinese wedung or like Alan G. Maisey write a "tiuk pengentas". Look this two threads where you can see very similar ones and as well some informations about this knifes:
http://www.vikingsword.com/vb/showth...ghlight=wedung,
http://www.vikingsword.com/vb/showth...ghlight=wedung
Nice one what you own, congrats for this nice find.
Regards,
Detlef