101Leafy researched the games.
ImperialGunHmmrSpark

A covered lock improves the accuracy of this expensive customization upgrade.
A fine piece that refines the mechanical hammer further and greatly raises its power. There is a story that a certain country, taking note of its destructive force and technical quality, asked the workshop to make it the standard gear of its royal guard. Because of the high cost, every one is made to order.
Our translation of 復刻 ハンター大全 (KADOKAWA / Enterbrain, 2014), page 156.
| Class | Hammer |
|---|---|
| Rarity | 10 |
| Attack | 1248 |
| Fire | 540 |
| Slots | 2 |
| Table price | 120,000z |
Upgrades
| Upgraded from | Regulation GunHammer |
|---|
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.