7b23a9de_Item_Rarity___Dead_Island_Wiki__Description
[Rarity] Unique, Superior (Riptide) purple text [Reward] Yes [Chests (weapons)] Metal/Locked chests Low [Looted (items)] No [Dropped (zombie)] Yes Very Low [Description] 
Can be given as a reward from quests, or rarely found in chests and on corpses.
Item Rarity - Dead Island Wiki