This is a tuckbox for the cards in the FRED/Gryphon printing of the game. The box has a little more depth than is necessary to hold just the cards, and this is so you can print out a one-page sheet of the rules and cut and fold it down to size to fit it in the box. This way, you can carry the whole game in the tuckbox and save a lot of valuable space, since the box the game comes with is about 10 times larger than necessary. The box was made with the help of the tuckbox generator at http://tuckbox.gameupdates.com/
and images from here at BGG.