Earlier quoted context omitted.
That old problem has of course been addressed, e.g. by using things like gold certificates: https://en.wikipedia.org/wiki/Gold_certificate Which add their own set of problems, but at least you get a clear signal when they get repudiated. Or you use banks, letters of credit from them ( https://en.wikipedia.org/wiki/Letter_of_credit ), etc.
Except Gold Certificates are fake money. Many crashes in the 1800s were about Banks issuing too many certificates for the amount of Gold that was actually stored in their vaults. Gold Certificates are no different than credit cards or fractional reserve banking. The bank makes a promise without proving anything, and people are expected to trust the banks for things to work out. And when the poop hits the fan, people…
Which might be why I said:
but at least you get a clear signal when they get repudiated.
When, not if. I think this may be better than how fiat money "works", but obviously opinions vary.