New Delhi, April 14 -- There is angst in the air about the US dollar's once and future global role. For insight into the greenback's prospects, pundits have looked to the British pound sterling, the dollar's predecessor as the dominant international currency, and asked how economic stagnation, heavy debts and failed geopolitical adventures, like that in Suez in 1956, conspired to rob it of its global role.

But informed observers can draw on a much longer history of international currencies-units used in cross-border transactions-stretching from the Dutch guilder of the 17th and 18th centuries back to the Florentine florin of the 14th and 15th centuries and the silver denarius of ancient Rome.

In fact, it can be argued that the Roman den...