Agricola cow spots stickers. Contained in Lookouts' magazine "Neues vom Ausguck" #12 (10/2018).
These 36 stickers can be placed on the cows of Agricola (Revised Edition) to distinguish them from the horses in Agricola: Farmers of the Moor. The cattle in some copies of Agricola and the horses in Agricola: Farmers of the Moor have the same color.
Of course the stickers can also be used to upgrade your game.