Nice kris.
I don't think you have a twisted core, but there seems to be some activity in the center. I would try to etch the blade a little with a vinegar solution to see what you've got there. If it doesn't look pretty it is easy enough to polish it out.
If you have the means you might want to test the asang-asang that appears copper. If it hasn't tarnished over time as copper is prone to do it is possible that the asang is actually suassa. Especially possible if the pommel and the rfittings are silver since that would show that some of some wealth once owned this sword.
If this were mine i would do a little bit of oiling an polishing on that wood as well to help bring out the tiger stripe wood pattern. This piece could look much better with a little "spit and polish" before gifting it to dad.
