IMF has this, intra-countries, with their SDR ("Special Drawing Rights"). China was added in the 2010s, and USD has slowly been losing its percentage of the SDR's overall-makeup.

[•] <https://wikipedia.org/wiki/Special_drawing_rights>

SDR's are a type of Keynes' "Bancor" concept, but only transactable between countries. Citizens may resort to the commoner's bancor, e.g. bitcoin (but also gold, silver &c).

[•] https://en.wikipedia.org/wiki/Bancor