101Leafy researched the games.
Bone Axe

Streamlined for easy swinging. Looks like an Axe, but it's actually a Hammer.
| Class | Hammer |
|---|---|
| Rarity | 2 |
| Attack | 624 |
| Affinity | 5% |
| Slots | 1 |
| Price | 2,150z |
Upgrades
| Upgraded from | War Mace |
|---|---|
| Upgrades into | Bone Broadaxe |
Upgrade tree from モンスターハンターポータブル 2nd G 公式ガイドブック (Enterbrain, 2008), page 720.