There are several special Nova Crystals that have been minted for special occasions. These are listed here along with id numbers for checking if you are getting the genuine item.
First Nova Crystal
ID(s): 811950
This is the first Nova Crystal ever produced, and given to the Chairman of the IGBC at the time, Ellias Aubec.
Y13 Celebration Nova Crystal
ID(s): 2732213 – 2732232
These twenty Nova Crystals were minted to celebrate the 13th year of new calendar. Ten were reserved for Krath citizens, and the other ten were auctioned off to the public.