Other items inside the chest include wanted posters for all the Borderlands 2 playable characters (including the DLC ones, which the previous chest did not). There's also some pretty neat crumpled up newspaper pages that act as packaging materials but you quickly realize are even more bonus content, since they're actually from a newspaper written by characters in the game. Also, some window decals.
The chest itself is pretty solid. Which is good, because the cost for the whole package is $100. If this was some flimsy plastic (like the mask) I'd be pretty pissed. But this thing could probably survive a few drops and I wouldn't mind using it as a toy chest for some collection or other.
Even cooler: the box the chest comes from simulates an in-game shipping box with additional jokes scrawled over it by various characters. It's pretty great.