"- but surely these aren't in fact unique, they're just unique locally? Actually it's a little odd you don't have any duplicates to start with, I guess people don't carry much cash..."

"Unique in this court, or maybe unique in faeryland. I think things we can't get at don't matter much. If you dropped those in the ocean I'm sure they'd stop affecting anything."

"Huh. - I wonder if bills with different serial numbers distinct only in that way would count as unique."

"I don't know. .... we could test it."

American dollar bill and a fresh graph.

The universe thinks that this object is not very valuable. "I think the paper'd be worth more without the markings."

"Maybe it's because it's fiat and the issuing government is not nearby."

"That might do it."

Does the system like solid copper pennies?

Likes them better than the dollars.

"That's funny because the bill is supposed to be worth a hundred of these."

"If we set up a government willing to exchange the bill for a hundred of the coins it'll be worth more. Not a hundred times more, though, I don't expect."

What does the system think of quarters and dimes and nickels?

Orders them by the value of the metal (nickel, quarter, penny, dime).

"Huh. I assume when these denominations were issued it was connected to the metal's scarcity at the time, but this isn't the order of their value..."

"When were they issued?"

"I'd need to look it up. Hundreds of years from now. But none of them are aluminum, that's the one I know gets way easier to get ahold of in the future."

"I don't know what this is going off. Faeries don't make much use of metal."

What does the system think of this aluminum coin Cam just made up?

Very impressive!

"If it likes aluminum, it might be deriving some information from current human mining capacities. Like, after aluminum gets easier to handle it's not hard to find and people use it for disposable drink containers."

"Huh. 

I think if you were to have a currency faeries used, you'd want a metal that can't be mined anywhere, if there are any of those, and varied beautiful designs with no two the same, and then once you had enough of them almost all of its value would be from stable sources of value and people could predict how much they were worth."

"There are metals you have to synthesize but they're radioactive, which might be harmless to you, I don't know, but could harm nearby human and animal and plant populations. Also they decay into other metals over... time periods that might conceivably be functional at this speed, if it were ever useful to have your money diminish by half every thirty realtime hours, or something?"

"That sounds really neat but not at all useful for this purpose. - what about the metal that made the balls in your cage, is that mined?"

"I think so, though it's rare. Why, is it valuable?"