IMF, which knows an inconvertible currency when it sees one, pays them solemn respect.

ECONOMIST: Global poverty

There would be nothing like the same confidence, by the public generally, in an inconvertible currency so regulated, as in a convertible one: and the most instructed person might reasonably doubt whether such a rule would be as likely to be inflexibly adhered to.

FORBES: The 10 Minute Gold Standard: It's Much Easier Than You Think

The Indian currency, the rupee, was inconvertible and high tariffs and import licensing prevented foreign goods reaching the market.

BBC: India: the economy

China is preparing for a world beyond the inconvertible paper dollar, a world in which the renminbi, buttressed by gold, becomes the dominant reserve currency.

FORBES: Signs Of The Gold Standard Emerging In China?