What Sub-class does it use?
Obviously Thrown is the base Weapon class but the table on page 51 of HARP Fantasy doesn't have War Hammer under thrown weapons. The sub-classes of Pole Arms Thrown, Thrown Blades & Thrown Projectiles don't fit. The first two just by name and Thrown Projectiles has a fumble range of 1-6 and covers boomerangs and bola etc....