Money is what money does.
It is possible to imagine that the dollar could be so badly issued at some stage in the future that it, too, would become as questionable as the zloty. Yes, I agree about gold and diamonds though, in practice, there's a great difference between them as regards perceived value. Gold has had perceived value going back to at least 4,000BC and most of its production is still hoarded by hundreds of millions of people. It's been de-throned by some central banks but we can be certain that it would gain instant universal value as a means of exchange if the major official currencies went down the pan together. Diamond's value in extremis is questionable because a substantial part of diamond production is withheld from the market and, in any case, can now be made artificially at a fraction of the cost of the present lot.