From Bulbapedia, the community-driven Pokémon encyclopedia.
A Coin Case (Japanese: コインケース Coin Case) is a key item used in each of the Game Corners scattered around the Pokémon world. A Coin Case has appeared in every main series Pokémon game until Pokémon Black and White, where the Coin Case and Game Corners are completely absent.
Red has 304 Coins in his Coin Case (picture from FireRed and LeafGreen)
The purpose of the Coin Case is to hold Coins, which are the currency of the Game Corners. If a player does not have a Coin Case, then he or she is not allowed to participate in the gambling-type games like slot machines and roulette, as Coins must be inserted into the game machines before play can begin.
The Coin Case can hold up to 9,999 coins in Generations I, II, and III, and up to 50,000 coins in Generation IV. If the limit is reached, no further winnings can be put in the Coin Case—they will simply be discarded—and no further coins can be purchased.
There are three ways to determine how many Coins are in a Coin Case. The first is to play a game at the Game Corner; by default, the total amount of Coins held will appear on the screen. Secondly, a player may inquire to buy Coins at the Game Corner counter: as with money, the amount will be shown in the corner of the screen. Finally, the player may use the Bag menu to examine the Coin Case. This will show the contents of the Case.
As a key item, the Coin Case cannot be sold.
- Main article: Coin Case glitches