A fiat currency is an ephemeral thing. From Jeff Thomas at internationalman.com:
In 1260, Kublai Khan created the first unified fiat currency. The jiaochao was made from the inner layer of bark of the mulberry tree. It’s of interest that the mulberry tree was quite common in Mongolia. What allowed Kublai Khan to get away with treating tree bark as currency was that each bill was cut to size and signed by a variety of officials. They affixed their seals to each bill. To further ensure authenticity, forgery of the chao was made punishable by death.
But even then, why would people accept bark as being of the same value as gold and silver, which had successfully served as “money” for thousands of years? Well, to begin with, the chao was redeemable in silver or gold. But just to make sure it was accepted, Kublai decreed that refusing to accept it as payment was also punishable by death.
Today, we’re more sophisticated. Governments no longer threaten to kill people for refusing to use a fiat currency; they just make it extremely difficult to deal in anything but fiat currency.
Had another fake $1 the other day, it looks like it has been through a washer with the large ONE faded and off the mark.
Self-checkout kept spitting it out, the clerk said what do you want to do, keep it for comparison.
Probably not worth the trouble unless you had a huge batch and went around converting.