WoWDB

This item came from the original WoW TCG.  Inside every pack of cards was a card that was worth a certain number of "points."  You could spend those points on a store website to buy certain in-game items like tabards and fun /use items.  This firework was one of those items.  It cost 30k points.

The TCG and associated points no longer exists in that incarnation, so this item is effectively no longer obtainable.

In Warlords of Draenor, this item will be added to the new Toy Box feature and no longer take up a bag slot.  You will be able to "use" the item straight from the Toy Box interface. 

The Toy Box will be account-wide and therefore so will this item.