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I'm going with Gugi based on the latest input from the OP.

Randydance had a brush made by Skip Nordstrom. He poured it and turned it on a wood lathe. It looks very similar to this..

I would say it is not bone.
But, saying it is not antiquated, it could be ivory.

I remember Pixel saying you had to use a metal lathe to turn ivory. Wood lathes produced a lot of chatter marks.