In Final Fantasy VI, this ability gives perhaps the only good visual representation of what a Gil coin looks like: a circular metallic coin with a small hole in the center with markings around it. This makes it visually similar to other, real-world currencies (most notably that of Japan, because it has the shade of a 5 or 50 Yen piece).

Final Fantasy Tactics contains an animation of gil as circular, golden coins when a Thief uses the Steal Gil ability. Final Fantasy XI also has a visual representation of gil in the form of normal gold and silver coins.
In these games, the coin could be seen as a generic symbol for money, such as the sword the FF series often uses as a generic symbol for weapons. As such, it is not neccesarily the image of the coin. The coins used in "throw coin" are also not neccesarily gil, as one with four quarters could be said to have a dollar, though a dollar is a rectangular slip of paper, and they have 4 circular disks. These are not proof.