you buy it in the game corner with coins after you get the coin case
So you can get the coin case from the lady in Mauville City.
In Mauville city
go to slateport and by 1 habor mail then go to the lady's house next to the game center and trade it with her.
First, you get a Harbor Mail. Anywhere. Then go to Mauville. Go to the house east/right to the game corner. Talk to the lady, trade the Harbor Mail and she'll give the coin case
you buy it in the game corner with coins after you get the coin case
So you can get the coin case from the lady in Mauville City.
you wait
In Mauville city
you can get is at mauville game corner but you will have to get the coin case first from the person inside the house beside the mart she will give you coin case for harbour mail which is at slateport.buy the TM in game corner
go to slateport and by 1 habor mail then go to the lady's house next to the game center and trade it with her.
First, you get a Harbor Mail. Anywhere. Then go to Mauville. Go to the house east/right to the game corner. Talk to the lady, trade the Harbor Mail and she'll give the coin case
You can only get one coin case.
nothing it was just an amulet coin
Go to the house next to the casino. When the lady says," I wish i had harbor mail" , go to the slateport Pokemart, buy harbor mail, go back and talk to her, and yes when she wants to trade you a harbor mail for a coin case.
In Pokemon Yellow, you can obtain the coin case from a man sitting at a table in the cafe in Celadon City. The purpose of the case is to hold coins for use at the Game Corner. In Pokemon Yellow, the Coin Case can hold up to 9,999 coins.
go to mom she will give you the amulet coin