I feel this 'material issue' is coming to a climax . . . . .! he he. On top of that I may come back from my opinion of it being bone as, when I look again at the pics- it could indeed be also tridacna.
Indeed I was not reverring to Santa's reindeer Thor but to the Philippine waterbuffalo called 'carabau' (as common with Phil. culture n items I assumed others know this term too).
Difficult to give directions/advise on this matter; can only say tridacna is like marblestone and bone would be alike very hard ebonywood (to give material comparisson).
Howabout this; tap the handle on glas n when it says 'TOK TOK' it is tridacna n when it does 'POK POK' its bone . . . . .
(not much of advise is it . .?!?!?)