1971 puts it a little too close to the present. Individuals haven't been able to convert notes to hard currency since June 5, 1933, when legal tender laws were introduced.
That said, I still agree with the thrust of your argument, that we're in new territory with regard to unbacked paper money.
> Individuals haven't been able to convert notes to hard currency
In the US! Well, the rest of the world had other worries back then anyway, and after WW1 + WW2 most of the world's gold was on US soil thanks to trade flows and custody deals and debts etc etc. Hard to keep a gold standard when all the gold is with one party for all intents and purposes ;)
That said, I still agree with the thrust of your argument, that we're in new territory with regard to unbacked paper money.