Interesting barung. I have a similar one I picked up years ago that was brought back from WWII by a serviceman engraved with his name and "Malabang Air Strip, Mindanao, P.I, April 17, 1945." Malabang is south of Lake Lanao and northwest of Cotobato so the Maranao attribution is most likely correct thought not a standard weapon among the Maranao (or Maguindanao for that matter.)
If your barung was made by the same craftsmen as mine, then I suspect that your blade has a double-edged tip
