In addition to the coins described above, the Mutant Lord could decide that whatever form of currency was common at the fall of the previous society is still in circulation. If this is the case, it will have a comparative value to these precious coins. This value could be more or less than that of coins, depending on how abundant the money is. In the wastelands of Mutant Future, money can be scarce.I still use the copper/silver/gold standard since it's fairly easy and established. The explanation I've internalized is that the inherent "value" of the coins is left over from before The Fall. The Ancients valued them, therefore the denizens of the Mutant Future also value them. And I would think that Ancient minted coins would have survived the apocalypse and would therefore be in use. Even if their usefulness is nil.
But over on the blog Aeons & Augauries, JDJarvis has come up with an elegantly simple coin system with a great internal logic: Alternate Coins for the Ruins. He posits that materials common and of value to the mutants would be in use as coinage materials. Plastic, lead, and uranium replaces copper, silver, and gold respectively. After all, who would want silver ingots in a radiated wasteland when lead can be used in radiation shielding and melted into bullets? I like this idea and it gives coins an actual use and value other than just "That's what The Ancients traded for goods and services." I'll be implementing this in my own games shortly.
Although, on the subject of "value," would gems, jewelry, and precious "treasures" be sought after by the Ruined Earth mutants or would they seek out more practical things like antirad-pills, gasoline, and other such items?
"Put those shiny marbles down and help me with this case of Spam!"