Armor Fossil is an item in the “Dex completion” category (Items). It costs ₽7000.
In-game descriptions
| Diamond / Pearl · Platinum · HeartGold / SoulSilver · Black / White · Black 2 / White 2 | A fossil from a prehistoric Pokémon that lived on the land. It appears to be part of a collar. |
|---|---|
| X / Y · Sun / Moon · Ultra Sun / Ultra Moon · Let’s Go, Pikachu! / Let’s Go, Eevee! · Sword / Shield | A fossil from a prehistoric Pokémon that once lived on the land. It looks to be from some kind of protective collar. |
Where to find it
Not placed on the atlas maps (so far: Red/Blue and Generation 3).
Sources : PokeAPI (items, item_flavor_text, machines) · atlas · pokeemerald species_info.h