FFX-2 actually has "ancient coins" that you dig from a desert and use on the Sphere Break minigame. I assume they were the gil used 1,000 years ago, when Zanarkand was still around..

There is also this scan a friend of mine did from his FFX Ultimania guide for me
http://ffproject.net/forumwiki/index...mage:Coins.JPG (scroll down)