Hundang knife/Mt. Pinatubo Negritos

[A. G. Maisey]

This type of bladed implement is totally outside my area of specific knowledge, however, the file work on the back of the blade is not.

In many societies across the world, file work on the back of a blade is put there to assist grip when working with a knife by holding with the "thumb on blade"grip. This grip is common in both working knives and knives used as weapons.