101Leafy researched the games.
Twin Shells

Sword made from two varieties of shell. Very good at keeping Sharpness.
| Class | Sword |
|---|---|
| Rarity | 9 |
| Attack | 336 |
| Defense | +20 |
| Slots | 1 |
| Price | 90,000z |
Upgrades
| Upgraded from | Dual Carapace+ |
|---|---|
| Upgrades into | Twin Shears |
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 704.