Usually the display cartridges have no primer or a struck primer to designate its being inert. In some cases the primer cup is blackened.
But another possibility for this cartridge is that it is a pressure test round, the hole in the case usually covered by cellophane tape to keep the powder in. The round would be loaded into a special barreled action that allowed a pressure transducer to be inserted into the case from outside the action. The gun is then fired and the transducer registers the pressure created. (There’s actually 2 ways to do this measuring using the hole in the case. For simplification, I’ll just leave the description at that.)