Aurelian’s reform and the riddle of XXI
In 274 Aurelian reorganised the coinage and had the new pieces carry two characters, XXI, whose meaning is still argued over. It was the first serious attempt to get out of the monetary crisis.
An empire stitched back together
In four years Aurelian beat the Juthungi and the Vandals, took Palmyra back from Zenobia, then recovered the Gallic Empire after the surrender of Tetricus. The legend RESTITVTOR ORBIS that then appears on his reverses is not an empty formula: territorial unity really had been restored.
The monetary reform came with that reconquest, and it was also an answer to the revolt of the Rome mint workers, harshly put down a few years earlier — a sign that the capital's mint had become uncontrollable.
What the reform changed
The weight of the silver coin was raised, its content brought to around 5 per cent, and the surface silvering made more regular. The mints were reorganised and their marks standardised, and modern numismatists call this reformed piece the aurelianus, for want of knowing its ancient name.
The gold coinage was put back in order at the same time, without reaching the stability Constantine would give the solidus forty years later.
The riddle
The letters XXI, or KA in the East, appear in the exergue of the reformed pieces. The most widespread interpretation sees in them a ratio of twenty to one between the bronze and the silver contained, in other words a guarantee of fineness displayed on the coin itself. Other readings have been proposed: a face value of twenty sestertii, or an indication of alloy meant for the mints.
No ancient source settles it. It is a good example of what numismatics can establish — composition, chronology, distribution — and of what, in the absence of a text, it can only hypothesise.
A relative failure
The reform did not restore confidence. Prices went on rising, which Diocletian's price edict would try in vain to freeze in 301. But it set a model: a silvered bronze coin of controlled fineness, which the Tetrarchy would take up with the nummus.
Further reading
S. Estiot, work on the coinage of Aurelian and the publication of the Venèra hoard, the current reference on the reform.
A. Watson, Aurelian and the Third Century, London, 1999.
J.-P. Callu, La politique monétaire des empereurs romains de 238 à 311, Paris, 1969.