101Leafy researched the games.
Shell Castanet+

One blow causes the claw to hit against the shell, making a unique sound.
| Class | Hunting Horn |
|---|---|
| Rarity | 9 |
| Attack | 1144 |
| Water | 240 |
| Defense | +15 |
| Slots | 0 |
| Price | 85,000z |
Upgrades
| Upgraded from | Shell Castanet |
|---|---|
| Upgrades into | Bi-Colored Castanet |
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 740.