In the Kanto region, Celadon city contains a game corner like the one in Goldenrod. In the prize building to the left of the game corner there is a man in the top right corner that can identify the type of your pokemon's hidden power. In that same building; the person on the left can sell you the TM for hidden power for 6,000 coins. Also available for purchase in that same game corner are the following TMs: Endure, Double Team, Psychic, Gyro Ball, and Giga Impact. Mr. Mime, Eevee, and Porygon are available for purchase from the lady on the right. The coin case can be obtained from the man behind the game table in either Goldenrod city or in Celadon city. The single coin case works for both cities and there are also more items/pokemon available for purchase in the other game corner in Goldenrod city, but the people that sell you them are in the game corner building. To my knowledge; playing the game with the man and winning is the only way

to earn coins.