Doubloon

"This is a Doubloon. They are the only currency accepted in Jolly Roger's Lagoon."

- Jamjars

Doubloons are currency used in Jolly Roger's Lagoon. They are golden coins with the imprint of a in them.

Banjo-Tooie
In Banjo-Tooie, 30 Doubloons can be found scattered throughout Jolly Roger's Lagoon. They can be spent at Jolly's to buy a room and learn the Sub-Aqua Egg Aiming from Jamjars, at Pawno's Emporium to buy a Jiggy and a Cheato Page, and at Blubber's Waveracer Hire to buy a pair of Turbo Trainers.

Collecting all 30 Doubloons unlocks a gamer picture in the Xbox Live Arcade release of Banjo-Tooie.

Banjo-Kazooie: Nuts & Bolts
In Banjo-Kazooie: Nuts & Bolts, Captain Blubber mentions in Showdown Town that he went "Doubloonless" after crashing the Saucer of Peril near the Uptown district.

Trivia

 * Despite Jamjars stating in Banjo-Tooie that the Doubloons are the only currency accepted in Jolly Roger's Lagoon, the menu of Jolly's uses signs ($).