Yes Wullie !! It is always a pain for me !!
Ivory is a very fine grain, and it shows a cross hatched pattern along with a few other characteristics that I don`t see on yours !! And not all resins will melt with the hot pin !! There are some that use ground bone as well as stone or marble with the resin !! More difficult to tell !! Will not hurt to try the hot pin though !!
And that AB mark on yours is usually how they mark a two part epoxy resin,,(part A and part B) !! You would think it was a sculptors mark but it isn`t !! It is simply known as AB Resin !!