Item data structure in Generation III

Item data is stored in a 44-byte structure in the US version of the GBA games.

Pocket
This determines which pocket of the Bag the item should be stored in. This does not prevent the item from being in another pocket, though. The game uses it to see where it should place the item upon collection.

For FireRed and LeafGreen

For Emerald, Ruby and Sapphire

Type
For items other than Poké Balls, the type determines how the item can be used. With Poké Balls, the type indicates the Poké Ball type, and is one less than the index number.

Parameter
A parameter used by different kind of items. It is used to represent the number of steps repels and flute effects last. HP and PP recovering items have this value as their number of HP/PP recovered, but the actual number of HP/PP restored is stored in a different table.

Mystery values
Mystery value 1 is:
 * 0 for normal items.
 * 1 for HMs and most key items.
 * 2 for some plot-related key items: Blue Orb, Devon Goods, Letter, Oak's Parcel and Red Orb.

Mystery value 2 is:
 * 0 for most items.
 * 1 for many key items: Acro Bike, AuroraTicket, Berry Pouch, Bicycle, Fame Checker, Good Rod, Itemfinder, Mach Bike, Magma Emblem, MysticTicket, Old Rod, Old Sea Map, Pokéblock Case, Powder Jar, Rainbow Pass, Ruby, Sapphire, Super Rod, TM Case, Tea, Teachy TV, Town Map, Tri-Pass and VS Seeker.

Battle usage
Battle usage can be:
 * 0 if the item can't be used in battle at all.
 * 1 if the item's effect is seen during battle but on a subscreen, such as healing items.
 * 2 if the item's effect is seen in battle such as Poké Balls.

Extra parameter
Extra parameter is used to distinguish Poké Balls and Mails, as opposed to just using the item index.

Offsets
These are for US Versions:
 * Ruby: 0x083C5564
 * Sapphire: 0x083C55BC
 * Emerald: 0x085839A0
 * FireRed: 0x083DB028
 * LeafGreen: 0x083DAE64

Fingerprint
For Ruby/Sapphire: AC AC AC AC AC AC AC AC FF 00 00 00 00 00 00 00 00 00 00 00 DA 55 3C 08 00 00 01 04 11 A7 0C 08 00 00 00 00 00 00 00 00 00 00 00 00 // ???????? C7 BB CD CE BF CC 00 BC BB C6 C6 FF 00 00 01 00 00 00 00 00 A0 20 3C 08 00 00 02 00 00 00 00 00 02 00 00 00 65 A2 0C 08 00 00 00 00 // MASTER BALL CF C6 CE CC BB 00 BC BB C6 C6 FF 00 00 00 02 00 B0 04 00 00 D3 20 3C 08 00 00 02 01 00 00 00 00 02 00 00 00 65 A2 0C 08 01 00 00 00 // ULTRA BALL C1 CC BF BB CE 00 BC BB C6 C6 FF 00 00 00 03 00 58 02 00 00 0D 21 3C 08 00 00 02 02 00 00 00 00 02 00 00 00 65 A2 0C 08 02 00 00 00 // GREAT BALL CA C9 C5 1B 00 BC BB C6 C6 FF 00 00 00 00 04 00 C8 00 00 00 44 21 3C 08 00 00 02 03 00 00 00 00 02 00 00 00 65 A2 0C 08 03 00 00 00 // POKE BALL CD BB C0 BB CC C3 00 BC BB C6 C6 FF 00 00 05 00 00 00 00 00 6B 21 3C 08 00 00 02 04 00 00 00 00 02 00 00 00 65 A2 0C 08 04 00 00 00 // SAFARI BALL C8 BF CE 00 BC BB C6 C6 FF 00 00 00 00 00 06 00 E8 03 00 00 A0 21 3C 08 00 00 02 05 00 00 00 00 02 00 00 00 65 A2 0C 08 05 00 00 00 // NET BALL BE C3 D0 BF 00 BC BB C6 C6 FF 00 00 00 00 07 00 E8 03 00 00 D7 21 3C 08 00 00 02 06 00 00 00 00 02 00 00 00 65 A2 0C 08 06 00 00 00 // DIVE BALL C8 BF CD CE 00 BC BB C6 C6 FF 00 00 00 00 08 00 E8 03 00 00 0F 22 3C 08 00 00 02 07 00 00 00 00 02 00 00 00 65 A2 0C 08 07 00 00 00 // NEST BALL ...