Doubloons

Doubloons are a currency won from Treasure Hunter – Talk like a Pirate Day! event, from killing any pirates, from pickpocketing NPCs, and by training Agility at Brimhaven, that can be exchanged for pirate-related items. (These are different from Pieces of Eight obtained from the Trouble Brewing mini-game.)

When killing pirates, you can receive the message, and have them automatically added to your inventory.