Hi Longfellow,
I'm sorry for not getting back to you on the hilt material any time sooner - I must have missed your update somehow.
The scale is a bit tricky to ID, with those diagonal scratches in the surface obscuring the grain, but two features prompt me to believe that we're looking at rhinoceros horn: The horizontal thread-like grain of the handle, where the individual fibers are visible in areas where the surface scratches aren't so prominent, is typical for rhino. Likewise, if you look at the hole drilled near the pommel, the edge is damaged in a way that looks more "thready" than "flakey". Old rhino horn when dry and damaged becomes this way, rather than break of in chips and flakes like many bovine horn, for instance.
But, it
is really hard to tell from photos!
Best wishes, - Thor