You found an uncommon loot box! You can see what's inside by opening it from your inventory, after you opened the loot box all currency and items should be in your inventory.
Uncommon loot boxes are less commonly found but are not super rare, uncommon loot boxes can have a variety of currency, items, collectibles and other game goodies that you can use within the game. Uncommon loot boxes can still be a hit or miss from time to time as some of them have less interesting content.
Loot boxes cannot be sold but can be traded or gifted to other users.
