The item that mob's taken can not be superimposed by others.

I killed an Enderman and it's dropped an EnderStone.(might be some plugin in server.)
Suddenly, a zombie come away, it pick up the EnderStone.
and I killed that zombie, the EnderStone come dropped once more time.
I pick up that, and it's show English name (but my default language of Minecraft is Chinese), and can not superimposed by others.