Frozen banner
From YPPedia
The frozen banner is a miscellaneous booty item awarded to all pirates at the time of the ocean merge. It is named for the pirate's originating ocean, for example "Frozen Midnight Banner", and can be cracked open or trashed. When cracked open, it produces a trophy commemorating the pirate's original ocean and an inter-archipelago chart of one of the two routes connecting the old oceans. The frozen banner is not tradeable.