Caligula Bronze Sestertius, RIC I (second edition) Gaius/Caligula 51

Monetary and Denominational Context

The sestertius occupied a central position within the Augustan monetary system as the premier large-module brass denomination, struck in orichalcum (a bright golden copper-zinc alloy) at an official tariff of four asses or one quarter of a silver denarius. Because of its expansive surface area, usually measuring approximately 35 to 37 millimeters in diameter with a nominal weight standard near 27 to 29 grams, the sestertius served as an optimal medium for high-relief ideological messaging aimed at the urban populace of Rome and the broader western provinces. Under Gaius (Caligula), whose reign lasted from AD 37 to 41, bronze production received renewed focus after decades of selective output under Tiberius. Caligula utilized base-metal coinages to broadcast dynastic filial piety, honors for deceased family members, and the staging of grandiose public religious ceremonies. Type RIC 51 constitutes the culmination of the emperor's iconic Pietas series, produced near the end of his principate to emphasize his dutiful adherence to ancestral religious ritual and senatorial cooperation, even as historical accounts reflect increasing personal tension within the capital.

Mint Location and Technical Production

Production of RIC I (second edition) Gaius/Caligula 51 is securely assigned to the principal imperial mint at Rome. Unlike early bronze coinages of the reign that numismatists once speculatively associated with western provincial branch workshops such as Lugdunum, meticulous die-link analyses and stylistic comparisons of Julio-Claudian dies affirm that the entirety of Caligula's official sestertius production was concentrated at the capital. The production process involved casting heavy orichalcum flans, heating them to soften the metal, and striking them between engraved bronze or iron dies under considerable mechanical force. The obverse and reverse designs exhibit the high artistic standard characteristic of master celators at Rome, marked by refined drapery on Pietas and architectural perspective across the temple pediment. The presence of the letters S C (Senatus Consulto) reflects the formal constitutional role of the Senate in sanctioning aes coinage, though artistic direction and mint output remained firmly responsive to imperial initiative.

Obverse Iconography and Variations

The obverse of RIC 51 stands out among early imperial sestertii because it deliberately departs from the customary convention of displaying an imperial bust or portrait head. Instead, the design presents the personification of Pietas seated toward the left upon an ornamental stool or throne. She is draped and veiled, embodying ritual purity, and extends a patera in her right hand as an emblem of libation and sacrifice. Her left elbow rests securely upon a diminutive draped statuette, traditionally interpreted as one of the virtues or the Graces, set upon an upright pedestal or basis. In the exergue beneath the ground line, the identifying word PIETAS anchors the composition. Surviving dies show slight artistic variations in the execution of the drapery folds, the proportions of the diminutive figure on the base, and the exact positioning of the lettering relative to the outer beaded border, yet the overall compositional schema remains strictly uniform across the emission.

Reverse Iconography and Architectural Detail

The reverse of type 51 offers an elaborate architectural and ritual scene centering on the hexastyle Temple of Divus Augustus in Rome. The temple is shown in front view, featuring six Corinthian or Ionic columns supporting an architrave hung with festive garlands. The pediment contains sculptural decoration, while the roofline is adorned with acroteria and surmounted at the summit by a prominent triumphal quadriga. In the foreground directly before the podium, Emperor Caligula is depicted performing a solemn religious sacrifice. Veiled in the traditional manner of a Roman priest (capite velato) and wearing a formal toga, he holds a patera over a garlanded altar placed on the right. He is assisted by two sacrificial attendants (victimarii): one leads a sacrificial bull toward the altar, while the second stands upright holding a patera or ritual vessel. Across the field above the temple, the dedicatory inscription DIVO AVG honors the deified Augustus, while the letters S C appear in the lower field or flanking the altar. Minor die variations occur in the detailing of the pedimental figures, the spacing of the garland swags, and the posture of the attendants leading the victim.

Epigraphy and Legends

The legends on RIC 51 convey a cohesive political and religious statement. The obverse legend reads: C CAESAR DIVI AVG PRON AVG P M TR P IIII P P, with PIETAS placed in the exergue. This expands epigraphically to 'Caius Caesar Divi Augusti Pronepos Augustus, Pontifex Maximus, Tribunicia Potestate IIII, Pater Patriae', identifying the issuer as Gaius Caesar, great-grandson of the deified Augustus, Augustus, Chief Priest, invested with tribunician power for the fourth time, Father of the Fatherland. By highlighting his descent as 'DIVI AVG PRON', Caligula anchored his legitimacy directly in his bloodline to Augustus rather than through his adoptive ties to Tiberius. The title 'P P' (Pater Patriae), accepted early in AD 38, is consistently retained. On the reverse, the legend DIVO AVG ('To the Deified Augustus') makes clear the dedication of the temple and the imperial sacrifice, while S C ('Senatus Consulto') formalizes senatorial approval of the bronze currency.

Typology and Chronological Sequence

Within the typology of Caligula's coinage established in the Roman Imperial Coinage, the Pietas and hexastyle temple sacrifice sestertii constitute an evolving sequence differentiated by the emperor's tribunician numeral. The design was first struck in AD 37 to 38 without a tribunician number or with TR POT (RIC 36), reissued in AD 39 to 40 with TR P III (RIC 44), and updated finally in AD 40 to 41 with TR P IIII, catalogued as RIC 51. Caligula entered his fourth tribunician year on 18 March AD 40, and this fourth power ran until his assassination on 24 January AD 41. Thus, type 51 was struck exclusively during the final ten months of his reign. The reverse scene has long been linked by historians to the completion and formal dedication of the Temple of Augustus, an undertaking begun under Tiberius and concluded by Caligula in late AD 37. Although the dedication occurred years earlier, the repeated re-striking of the type demonstrates its enduring utility as the regime's foremost public monument on bronze coinage.

Circulation, Survival, and Deposition

As high-value base-metal pieces, sestertii of RIC 51 entered widespread circulation within Italy and across the western Roman provinces, particularly in Gaul, the Rhine frontier, and the Iberian Peninsula. Because Caligula's reign terminated violently with his assassination and a subsequent informal damnatio memoriae, many of his bronze coins suffered deliberate defacement, countermarking under Claudius, or withdrawal and remelting. Despite these systematic destructions, substantial numbers survived in long-term monetary circulation, often persisting alongside the bronze coinages of Claudius and Nero until the Flavian period. Hoard contexts demonstrate that sestertii of Caligula were carried in circulation for decades, frequently showing extensive handling wear before ultimate deposition in military river finds, temple votives, or urban cash hoards.

References

1. Coins of the Roman Empire in the British Museum, Volume I: Augustus to Vitellius. pp. 156-157, nos. 69-72
2. Online Coins of the Roman Empire: RIC I (second edition) Gaius/Caligula 51. ric.1(2).gai.51
3. The Roman Imperial Coinage, Volume I: From 31 BC to AD 69 (revised edition). p. 112, no. 51