Colt Express: Rock Promo
A promo from the 2016 Easter Basket (Brettspiel Osternest).
It consists of a small folded board with the following instructions:
"This Rock decoration can be used to place your common deck during your Colt Express games, with or without the third expansion < Indians & Cavalry >, due to be released October 2016.
For more information, visit the BGG listing.