A Burning Sea Note.
A Burning Sea Note, also referred as BSN. Each Burning Sea Note can be redeemed for 300 Burning Sea Points. Burning Sea Points can be used to purchase items, ships, and more in the Treasure Aisle (TA) store!
Burning Sea Notes can be bought for real money in the Burning Sea Note Store, at https://burningsea.com/store
This item can also be traded to other players, or listed on the Auction House.
A Burning Sea Note (BSN) can be found in your Special inventory.
This information is provided by the update that PotBS Wikia is undergoing, by Captain Vuur.