Vindictive Harpoon

[Kaylessa]

In the Skulls and Shackles adventure path there is an item called: Vindictive Harpoon. Its a +1 harpoon and under the monster that is using it says that it does 1d6. A normal medium size harpoon does 1d8.
Here is the stat block for the harpoon under treasures:

Aura moderate transmutation; CL 9th
Slot none; Price 10,305 gp; Weight 16 lbs.
DESCRIPTION
This +1 returning harpoon (Pirates of the Inner Sea 18) is
made from the jagged, scrimshaw-carved tusk of a narwhal
attached to a 50-foot length of woven sinew. Unlike most
thrown weapons, a vindictive harpoon functions as well
underwater as on land, and its wielder takes no penalties on
attack rolls underwater.
CONSTRUCTION
Requirements Craft Magic Arms and Armor, freedom of
movement, telekinesis; Cost 5,305 gp.

Now I looked up the stats for a harpoon in the Pirates of the Inner Sea book, pg 18, and it says that a medium sized harpoon weighs 16lbs. So the stat block above has the weight of a medium weapon but the stat block under the NPC says it does small creature damage, 1d6. What gives!? Do magic weapons auto-size like magic armor in Pathfinder? Or am I missing something.

Thank you for any help.

[Doomed Hero]

Specific trumps general. It is a special item and its sized weird.

[Shaun]

For simplicity's sake, I always have all magic items size to their user as a part of their enchantment. If you don't so that, small PCs really have a hard row to hoe in published modules, generally speaking.

[Kaylessa]

Thanks !

[Cevah]

Ivory is a special material.

Ivory:

Bone can be used in place of wood and steel in weapons and armor. Other animal-based materials like horn, shell, and ivory also use the rules for bone weapon and armor. The cost of a bone weapon or bone armor is half the price of a normal weapon or armor of its type.

Weapons Light and one-handed melee weapons, as well as two-handed weapons that deal bludgeoning damage only, can be crafted from bone. Hafted two-handed weapons such as spears can be crafted with bone tips, as can arrowheads. Other two-handed weapons cannot be constructed of bone. Bone weapons have half the hardness of their base weapons and have the fragile weapon quality. Masterwork bone weapons also have the fragile quality, but magic bone weapons do not. Bone weapons take a –2 penalty on damage rolls (minimum 1 damage).

The weapon should be 1d8-2, but they made it 1d6 instead.

/cevah

[Paladin of Baha-who?]

The harpoon does 1d6 in the hands of the NPC who is using it because said NPC is size small. If you want to say it can resize to the hand of the person using it, that's fine, but otherwise it is a small-sized harpoon.