From the EVE Dev Blog:
The theme of the Second Decade is not only to celebrate the rich history of the first ten years of EVE Online, but also to provide our loyal fans with special access CCP’s future products and offerings. To that end, the CCP Mystery Code is your ticket to VIP benefits both now and for years to come.
So, without further ado, what can a CCP Mystery Code holder look forward to?
First off, I’m pleased to announce that as soon as you have opened your box and redeemed your Mystery Code, you will receive one bright and shiny PLEX which you can use to convert into game time, to trade in the market for ISK and much much more…