The 100 Gold Coin's only appearance was in Wario Land: Super Mario Land 3. In this game there are three different types of coins. This includes a single Gold Coin that gives Wario one coin, a 10 Gold Coin that gives Wario ten Gold Coins, and the rarest, the 100 Gold Coin that gives Wario 100 Gold Coins.
They look just like the single Gold Coins, but are bigger. These Gold Coins then determined what kind of house Wario would buy after he completes the game.