In keeping with the theme of the game, the gold case is modelled after Mario's iconic golden coins. It can be used to store small items, including the New Super Mario Bros 2 game card.
The upcoming platform sequel features new items such as the Gold Block power-up, the Gold Ring collectible and Gold Mario, who can throw gold fireballs that transform blocks and enemies into coins.
It also contains Coin Rush, a new high-score mode, in which scores can be shared and challenged via StreetPass.
Additional Coin Rush levels will be added to the game as post-launch DLC.
It was recently revealed that New Super Mario Bros 2 will feature two-player co-operative play.
The entire single-player campaign will support two players in New Super Mario Bros 2, with one player controlling Mario and the second as Luigi.
When playing co-operatively, the camera will follow whichever player is in the lead, with the second player turning into a bubble if they do not keep up.
New Super Mario Bros 2 will launch in PAL territories on August 17, two days before its North American release.
Watch a trailer for New Super Mario Bros 2 below: