The perfect shell is an item dropped by a Tortoise.
It is unable to be turned into a bank note, preventing more than 28 being turned in at a time.
It is not tradeable, but can be sold to Barlak in Dorgesh-Kaan for 600 coins and 500 Crafting experience.
Dropping monsters
Monster Combat level Quantity Rarity Tortoise 79; 92 1–3 Rare