This is a drop from Tortoises found at the Khazard Battle Field south of West Ardougne, in the small field north-west of the Grand Tree, or in the sewer slayer dungeon.
Uses:
Can be sold for 600gp to Barlak in Dorgesh-kaan. Can be used as a secondary ingredient to make a War tortoise pouch.
Notes:
Barlak is at the north end of the corridor located south-west of the marketplace. See the mini-map link below.