I don't feel this is anything but Elephant ivory where the sampir is concerned... looking at the hulu, I suspect the same source.
I've a much bigger Sundang sampir with the same external recess seen on the one face. Unlike this example, it is a single piece. This led me to some deeper study some time ago, simply because of the size, I could see no other option other than tusk. Digging in to Sperm whale teeth, the largest sizes and the hollow underside just didn't add up.
Here are some images and a good article from which one of the images was drawn from for this thread.
Gavin
Linky;
https://static1.squarespace.com/stat...2020+tusks.pdf