(Return of the roman d20. It surfaces at least once a year. ;-) )
The markings are not astronomical. They are ordinary (for the time) greek letters*, used as numerals.
Greek was the common language in Alexandria (Egypt) at the time (and the die is not 'Roman', but Egyptian from roman times).
Greek letters doubled as numerals.
So, nothing strange. It's a d20 numbered 1-20 in the mode common to the era and place it is from.
It's not particularly unique. The Louvre in Paris has several. I suppose British Museum also has a few hiding somewhere.
Several religious and mystic groups and practices used both dice and numbers as ways to divine the future/come close to the gods/infinity. Mostly d6's were used, but others got some love as well – the d12 is particularly useful for astrological if you stick to a post-babylonian system.
(Plato was in this, as much else, influenced by the pythagoreans, who may have used the 'platonic' solids as dice. They certainly knew of them, though Plato popularised them.)
I really like the old d20. My only gripes about this is that:
a) we only ever get the same picture (the one used when it was auctioned out in 2003, when it went for, IIRC, U$ 40 000.
b) No one makes replicas. Even in plastic.
[/End of the usual rant about the roman era d20. A labour of love. ;-) ]
discovers a lost dinosaur.
