Hi Lou:
Both the T'boli and Bagobo tribes of Mindanao use knives of this shape and the scabbards are similar. Mostly these are work knives or "women's knives." There is a picture of a very similar knife to yours in the booklet,
Tagabawa Bagobo, by Sonia Mangune (p. 39). The caption reads "SANGNGI Bagobo Knife."
Krieger's Plate 13 (no. 3) has another example labeled as a woman's knife, Bagobo. See here:
http://www.vikingsword.com/rila/krieger.html
Ian