Hi Robert,
That spear looks much better now that you have removed the rust. It is now a "happy" spear
This type of spearhead was used throughout the Northern Luzon Cordillera. They are popular among the Bontoc Igorot, Ifugao, Gaddang, Kalinga, Tinguian, Isneg, Applai, Ilongot, Isinay, etc. One notices that the shapes of the this type of spearhead have subtle differences. There are various terms used to call this spear, based on such differences. For example, if assuming that your spear is Bontoc, then it would be called "Pinilipo" because the neck is more or less cylindrical; as opposed to the "falfeg" which has four corners.
My best guest is that your spear is Ifugao, and it is a "Balabog" (generic term for a spear with such two prongs), but more specifically, it is a "Punol" (owing to the circular neck which gets thicker at the base).
I hope that this information was useful.
Nonoy