Historical Context

Macrinus became emperor after Caracalla's assassination in April 217 CE. His young son Marcus Opellius Diadumenianus received the subordinate title Caesar and the name Antoninus, associating the new ruling family with the prestige of the Antonine and Severan emperors. Denarii bearing Diadumenian's portrait therefore belong initially to the administration of Macrinus: the named prince was the intended successor, not a sole reigning emperor or the personal operator of the mint.

The Caesar coinage promoted succession, public hope, and the prince's association with the army. During the rebellion supporting Elagabalus in 218 CE, Macrinus elevated Diadumenian to co-Augustus, probably in May. This later status must be distinguished from his position as Caesar in 217. The regime collapsed after Macrinus's defeat near Antioch in June 218. Cassius Dio reports that Diadumenian, sent toward Parthia for refuge, was intercepted at Zeugma and killed. The surviving literary accounts differ in their details; they do not establish a quantitative explanation for the present survival of his denarii.

Obverse Iconographic Composition

The Caesar denarii show a youthful, bare-headed portrait of Diadumenian facing right. Catalogued bust variants are draped or draped and cuirassed, with the military breastplate visible beneath the cloak. These distinctions describe the engraved bust, and their visibility can be affected by wear and striking quality.

The Felicitas Temporum denarius naming Diadumenian as Augustus instead has a laureate, draped bust facing right. In this series, portrait and legend together distinguish the Caesar and Augustus issues. Differences in facial modelling alone do not establish a precise date or a separate mint.

Obverse Epigraphy and Inscriptions

The denarii carry Latin legends around the portrait. The following are catalogue transcriptions; spacing may vary.

  1. Caesar Titulature with the Antonine Name:
  • Lettering: M OPEL ANT DIADVMENIAN CAES
  • Expansion: M[arcus] OPEL[lius] ANT[oninus] DIADVMENIAN[us] CAES[ar]
  • Translation: "Marcus Opellius Antoninus Diadumenianus, Caesar"
  • Placement: Around the right-facing bust.
  1. Caesar Titulature without the Antonine Name:
  • Lettering: M OPEL DIADVMENIANVS CAES
  • Expansion: M[arcus] OPEL[lius] DIADVMENIANVS CAES[ar]
  • Translation: "Marcus Opellius Diadumenianus, Caesar"
  • Placement: Around the right-facing bust.
  • Catalogue example: RIC IV.2 107Aa.
  1. Augustus Titulature (218 CE):
  • Lettering: IMP CM OPEL ANT DIADVMENIAN AVG
  • Expansion: IMP[erator] C[aesar] M[arcus] OPEL[lius] ANT[oninus] DIADVMENIAN[us] AVG[ustus]
  • Translation: "Emperor Caesar Marcus Opellius Antoninus Diadumenianus, Augustus"
  • Placement: Around the laureate bust.
  • Catalogue example: RIC IV.2 118, following OCRE's transcription.

The Caesar legends identify an heir under Macrinus. The Augustus legend belongs to Diadumenian's brief elevation as co-emperor in 218 and must not be projected back onto the Caesar coinage.

Reverse Iconographic Composition

The principal reverse families connect the young prince with public hope, succession, and military allegiance.

  1. Spes Publica: Spes, the personification of Hope, walks left, holding a flower in her right hand and lifting her skirt with her left. The traditional image could associate the Caesar with hopes for the dynasty's future.

  2. Princeps Iuventutis: The prince appears in military dress with military standards. The catalogue family includes a standing figure holding a standard, with additional standards to the right, and a left-facing figure holding a baton and scepter, with two standards to the right. These are distinct compositions within the wider succession theme, rather than evidence that the child commanded the army.

  3. Felicitas Temporum: The denarius naming Diadumenian as Augustus shows Felicitas standing left, holding a cornucopia in her right hand and a long caduceus in her left. This conventional imagery advertises prosperity and good fortune; it does not demonstrate that peace had actually been restored.

Reverse Epigraphy and Inscriptions

The principal reverse legends are Latin and accompany the corresponding designs.

  1. SPES PVBLICA:
  • Lettering: SPES PVBLICA
  • Normalized Latin: Spes publica
  • Translation: "Public hope"
  • Placement: Around Spes.
  1. PRINC IVVENTVTIS:
  • Lettering: PRINC IVVENTVTIS
  • Title represented: Princeps iuventutis
  • Translation: "Prince of the youth"
  • Placement: Around the prince and standards.
  • The abbreviated PRINC does not by itself determine the grammatical ending; an expanded PRINCIPI legend would be dative.
  1. FELICITAS TEMPORVM:
  • Lettering: FELICITAS TEMPORVM
  • Normalized Latin: Felicitas temporum
  • Translation: "Good fortune of the times"
  • Placement: Around Felicitas.

Typology and Documented Variants

The following catalogue families describe the wider denarius series. They are not a complete die catalogue or a month-by-month emission schedule.

Caesar: Princeps Iuventutis Families (217-218 CE)

  • RIC IV.2 102 family: PRINC IVVENTVTIS with the prince holding a standard and accompanied by further standards. Precise bust subtypes require their full catalogue identifiers.
  • RIC IV.2 107Aa: M OPEL DIADVMENIANVS CAES; bare-headed, draped bust right. Reverse PRINC IVVENTVTIS, the prince standing left with baton and scepter, two standards to the right. Other members of the wider family use the Antonine name.

Caesar: Spes Publica Family (217-218 CE in OCRE)

  • RIC IV.2 116a: Bare-headed, draped bust right; M OPEL ANT DIADVMENIAN CAES. Reverse SPES PVBLICA, Spes walking left with flower and raised skirt.
  • RIC IV.2 116b: The same legends and reverse, with a bare-headed, draped and cuirassed bust right.
  • RIC IV.2 117: Also catalogued with a bare-headed, draped and cuirassed bust right and the Spes reverse. The shared short descriptions do not resolve every distinction between catalogue entries.

Augustus: Felicitas Temporum (218 CE)

  • RIC IV.2 118: Laureate, draped bust right; IMP CM OPEL ANT DIADVMENIAN AVG in OCRE. Reverse FELICITAS TEMPORVM, Felicitas standing left with cornucopia and long caduceus. This rare type belongs to Diadumenian's brief elevation as Augustus, rather than his earlier Caesar coinage.

Scholarly Debates and Attribution Limitations

Three limits matter when interpreting this series.

  1. Mint Attribution: The OCRE records cited here assign the Caesar denarii and the Augustus Felicitas Temporum type to Rome. Mint attribution is a catalogue conclusion, not information spelled out in their legends. Portrait differences should not automatically be treated as evidence for separate workshops. Clay's 1979 study is relevant to the coinage's classification, but detailed arguments require consultation of the study itself.

  2. Dating within 217-218 CE: The Caesar titles and the later Augustus title establish a broad sequence. OCRE dates the cited Spes types to 217-218 and the Augustus type to 218. A narrower monthly sequence may be proposed from die studies and other evidence, but the broad catalogue ranges do not establish exact beginning and ending months for each reverse.

  3. Rare Augustus Coinage: The Felicitas Temporum denarius documents the changed imperial title. Its rarity alone does not establish an exact surviving specimen count, a traveling mint, or how quickly news reached Rome. Such claims require an identifiable corpus or a specific scholarly argument. Likewise, political condemnation after the regime's fall does not by itself prove a systematic withdrawal of denarii or explain their modern survival rate.

Catalog Data

Ruler
DiadumenianWikidataNomisma
Denomination
Denarius
Material
Silver
Series date range
217-218 CE

Authority and vocabulary links: Wikidata and Nomisma.org.

References

  1. Online Coins of the Roman Empire (OCRE): Macrinus and Diadumenianus. RIC IV.2 Macrinus 116b; compare https://numismatics.org/ocre/id/ric.4.mcs.116a and https://numismatics.org/ocre/id/ric.4.mcs.117. Structured XML records checked for dates, legends and bust descriptions.
  2. Online Coins of the Roman Empire (OCRE): RIC IV Macrinus 118, Diadumenian as Augustus. ANS structured record https://numismatics.org/ocre/id/ric.4.mcs.118.xml: silver denarius, Rome, 218 CE; Augustus obverse and Felicitas Temporum reverse.
  3. Online Coins of the Roman Empire (OCRE): RIC IV Macrinus 107Aa. ANS structured record https://numismatics.org/ocre/id/ric.4.mcs.107Aa.xml: Caesar denarius, Rome, 217-218 CE; legend without ANT and standing prince with baton, scepter and standards.
  4. Clay, Curtis L., The Roman Coinage of Macrinus and Diadumenian. Clay's study: Numismatische Zeitschrift 93 (1979), pp. 21-40, pls. 4-5. Linked academic paper cites the study; it is not the study's full text. Exact emission dates and die-link arguments remain unchecked against the original.
  5. De Imperatoribus Romanis: Diadumenianus (217-218 A.D.). Donatien Grau, Universite Paris-IV-Sorbonne: Diadumenien (217-218 ap. J.-C.); Caesar under Macrinus, probable May 218 elevation as co-Augustus, and differing accounts of his death.
  6. Cassius Dio: Roman History, Book 79. University of Chicago-hosted Loeb translation; sections 34-40 on the rebellion, Diadumenian's elevation and the regime's fall. Book numbering varies between editions.