Is this a siraui?

[kai]

Hello Ian,

It feels much more natural in the hand if the knife is held with the sharpened edge up and the thumb resting on the end of the blade.

There are quite a few utility/EDC/status knives/tools which are mainly utilized with an edge-up grip: peurawot, lopah petawaran, luju celiko(?), piso raut, sanggi, etc.

Perhaps that is why the edge is not sharpened for the first few inches.

Yeah, for the first inch or so - 3.5" is quite a lot for human thumbs though!

A stab to the abdomen and a slice upwards would be a devastating wound and likely to hit major blood vessels.

That does work with a rencong hilt. However, with your piece the gripping hand would be much more likely to slip onto the blade (unless you lend support with the second hand - a risky strategy to bet your life on in a brawl, I'm afraid).

Regards,
Kai