Glass would have been expensive for a mere gambling device, whereas bone dice were cheap.
It's a Platonic solid found in Egypt, the epicenter of Neoplatonism.
And the symbols on the sides are astrological.
It might have been just an object of contemplation. Like, you can see how all of the heavenly bodies fit snugly into a perfect geometric figure and just wonder at it.
If there's any rhyme or reason to how the symbols are arrayed on the sides, it could have been a mnemonic or instructional device for casting horoscopes.
And, while it's probably too opaque to have been used for scrying, there's that too.
(Can take this to PM if you prefer).
Even mundane games played in taverns were magically bound to your luck and well-being. More sophisticated (board) games were outright sacred and were seen as a way to communicate with gods.