Caligula Copper-Alloy Dupondius

Monetary Context and Denominational Role

The monetary system inherited by Caligula in AD 37 was structured upon the bimetallic and base-metal reforms instituted by Augustus. Within this tariffing scheme, the dupondius served as an intermediate fractional unit valued at two asses, half an orichalcum sestertius, or one-eighth of a silver denarius. While the highest-value base-metal denomination, the sestertius, satisfied large civic payments and substantial domestic transactions, the dupondius performed an indispensable everyday commercial function in urban retail markets and military stipends. Under Caligula's predecessor, Tiberius, regular aes production at Rome had experienced prolonged interruptions, creating a regional scarcity of fresh fractional currency. Caligula met this pent-up monetary demand with robust emissions of orichalcum and copper coinage shortly after his accession. By deploying the dupondius alongside sestertii and asses, the imperial administration maintained clear visual and physical distinctions between denominations, reserving bright golden-hued orichalcum for the dupondius and sestertius, and redder copper for the as and quadrans.

Production, Mints, and Metrology

Scholarly consensus firmly attributes the standard imperial dupondii of Caligula to the mint of Rome. Early twentieth-century proposals suggesting auxiliary or provincial operations at Lugdunum (modern Lyon) have been revised in modern corpora, confirming that Caligula concentrated imperial base-metal manufacture in the capital. The dupondii were struck on prepared flans composed of orichalcum, an alloy of copper and zinc with minor trace elements of tin and lead. Surviving specimens demonstrate an intentional median weight standard ranging between 14.0 and 16.5 grams, with typical diameters measuring between 28 and 31 millimeters. The flans were cast in molds and struck with heavy iron dies aligned in an upright or inverted axial orientation. The distinct yellowish coloration of the fresh orichalcum alloy was critical for users to immediately differentiate the dupondius from the pure copper as, which was struck on planchets of comparable diameter but noticeably lighter weight standards.

Obverse Iconography and Variations

A defining characteristic of Caligula's dupondius series is the deliberate absence of his own portrait. Instead of presenting a radiate imperial bust, the obverse of the principal issue portrays Caligula's deceased elder brothers, Nero and Drusus Caesars, riding on horseback galloping to the right. Both riders are depicted wearing military cloaks that billow behind them, holding reins with their mounts in spirited motion. This equestrian iconography emphasized youthful vigor, military excellence, and dynastic tragedy, presenting the deceased brothers as model Julio-Claudian princes whose lineages were cut short under the previous regime. The radiate portrait tradition for dupondii during this reign was reserved for the consecrated founder of the dynasty, Divus Augustus, whose radiate head appears facing left on a companion issue accompanied by the flanking letters S C, explicitly reinforcing the sacred lineage connecting Caligula directly to Augustus.

Reverse Iconography and Compositions

The reverse design of the equestrian Nero and Drusus dupondius is austere and direct, dominated by the massive letters S C (Senatus Consulto) situated prominently in the center of the field. Surrounding this senatorial sanction is the circular inscription containing Caligula's full imperial titulature. The design purposefully eschews complex allegorical figures, focusing all viewer attention on the legal sanction of the Roman Senate and the living emperor who ordered the commemorative issue. Conversely, the radiate Divus Augustus dupondius exhibits a detailed figurative scene: the deified Augustus sits facing left upon an ornate curule chair, clothed in a toga and extending an olive branch in his right hand while holding a long scepter or patera. This tableau presents the divine progenitor of the empire in his dual capacity as triumphant restorer of peace and venerated patron of civil governance.

Epigraphy and Inscriptional Formulas

The inscriptional program on Caligula's dupondii functioned as an essential medium of political communication. On the equestrian obverse, the legend reads cleanly as NERO ET DRVSVS CAESARES, explicitly naming the two princeps iuventutis and affirming their posthumous honors. On the reverse, the peripheral inscription encapsulates Caligula's titles: C CAESAR AVG GERMANICVS PON M TR POT, periodically appended with specific consular or tribunician iterations such as COS or TR POT II. This title sequence translates to Gaius Caesar Augustus Germanicus, Pontifex Maximus, invested with Tribunician Power. On the Divus Augustus dupondius, the obverse legend is concisely formulated as DIVVS AVGVSTVS with S C across the field, while the reverse legend boasts the unprecedented formula CONSENSV SENAT ET EQ ORDIN P Q R, signifying the total harmony and consensus of the Senate, equestrian order, and the Roman people.

Typology and Chronological Sequence

Production of the dupondius under Caligula spanned the entirety of his four-year reign from AD 37 to 41. The primary equestrian type was initiated in the opening year of his rule (RIC I [2nd ed.] Gaius 34), bearing the initial tribunician title TR POT. As the reign advanced, the Rome mint executed subsequent die batches reflecting Caligula's updated constitutional positions, including issues struck between AD 38 and 39 with TR POT II (RIC 42), and a final phase during AD 40 and 41 incorporating TR POT III and TR POT IIII alongside his iterative consulships (RIC 49). The radiate Divus Augustus series (RIC 56) is generally situated within the inaugural emissions of AD 37 to 38, marking Caligula's dramatic arrival in Rome and his initial public spectacles honoring Augustus. Through these iterative strikings, the imperial authorities provided consistent supplies of fractional currency while reaffirming annual renewals of the emperor's legal powers.

Circulation, Hoards, and Archaeological Life

Archaeological finds across Roman Italy, the Iberian peninsula, Gaul, and the Rhine frontier reveal that Caligula's dupondii entered broad, active circulation throughout the western provinces. Because these coins bore the names and likenesses of the popular Germanicus family (Nero, Drusus, and Divus Augustus) rather than a direct personal portrait of Caligula himself, they largely avoided the violent physical defacement or chiseled damnatio memoriae frequently inflicted upon his sestertii after his assassination. Hoard evidence and site strata indicate that these dupondii continued to circulate through the reigns of Claudius and Nero, frequently accumulating extensive surface wear. In frontier legionary camps, specimens are often found countermarked with military stamps of subsequent decades, demonstrating that despite the short reign and catastrophic downfall of their issuing emperor, Caligula's orichalcum dupondii remained functional components of Roman daily commerce for generations.

References

1. Coins of the Roman Empire in the British Museum, Volume I: Augustus to Vitellius. pp. 146-160
2. Catalogue des monnaies de l'Empire romain, II: De Tibère à Néron. pp. 75-84
3. The Roman Imperial Coinage, Volume I: From 31 BC to AD 69 (Revised Edition). pp. 102-113