Tumbuk lada with Malayan rhino horn handle?

[Green]

Now that I have this item in hand, I'll putting up a few close up pics of the handle and part of the sheath. A rather unusual thing for me is the coloration of the handle, it is not black or translucent as in albino bufallo horn but brownish in parts and with lines/striations and pittings(?) in some places. It look almost like a skin rather than horn.

Can anyone comment what it actually is?... buffalo horn?