As part of the Kenway's Fleet content in Assassin's Creed Black Flag Resynced, one of the things you can obtain is Art Pieces. These items aren't the same as those found in certain treasure chests, and you'll need them for an achievement/trophy (you must collect all 19 of these treasures to unlock the Dilettante achievement/trophy).
To do this, you'll need to look for some very specific Kenway's Fleet missions.
To obtain these special items, you need to look for Brig missions (Schooner, Frigate and Man O' War missions don't offer these treasures) featuring the icon shown below.
The icon can take several different forms, but the reward will always be a single item (it will have a 1 beside it, and no other reward icon appears in a quantity of just one). This icon indicates that one of the mission rewards is a random Art Piece from among the 19 exclusive to Kenway's Fleet. Bear in mind that the available missions rotate randomly whenever you complete Kenway's Fleet missions, so you should check for new missions offering Art Pieces whenever you get the chance if you want to collect them all.
These are the 19 Art Pieces that can only be obtained through Kenway's Fleet missions. Bear in mind that you'll receive them at random, rather than in any particular order.
