Four Pillars Of Okie Culture

In James Blish's Cities in Flight tetralogy, interstellar trade by "Okie" flying cities is made possible by antigravity, anti-agathics and the germanium-based Oc dollar and is supplemented by the faster than light ultraphone and the instantaneous Dirac transmitter.

Antigravity is discovered in "Bridge" and anti-agathics in "At Death's End" and the Dirac is invented in "Beep" although, for reasons stated elsewhere, this story parted company with the Okie series.

That leaves the Oc dollar without an origin story. (I always thought that "Oc" must abbreviate "Okie" but it was never explained.) This currency matters because its collapse in the main Okie volume Earthman, Come Home (London, 1963) signaled the end of Okie culture. However, Blish does describe its origin in the Prologue to Earthman, Come Home.

Before space travel, germanium's importance for solid-state physics had made it fantastically valuable on Earth. Then:

"The opening of the interstellar frontier drove its price down to a manageable level, and gradually it emerged as the basic, stable monetary value of space trade. Nothing else could have kept the nomads in business." (p. 12)

That is all we are told: not enough for a story but the currency matters because, when it collapses, to be replaced by a drug standard, the Okies are finished and New York leaves the galaxy.

The advantages of the drug standard are:

drugs can be exactly valued by their therapeutic efficacy and availability;
cheaply synthesised drugs "...would be the pennies and nickels of the new coinage..." whereas rare, in demand drugs "...would be the hundred dollar units..." (pp. 121-122);
drug dilution could make debt payment flexible;
drugs, like metals, can be tested for counterfeiting;
rapid outmoding of drugs would prevent hoarding.

There would continue to be paper money but anti-agathic credits would raise the dilemma of using them to relieve poverty or continuing to live in poverty in order to live longer. It is no surprise when Blish's characters, like Poul Anderson's Master Merchants of the declining Polesotechnic League, decide to start afresh elsewhere. The fourth volume of Cities In Flight is set entirely outside the home galaxy where, of course, other problems arise.