The Usurper Usurped
Today's coin is a fairly scarce issue from AD 353 which comes with interesting history of the years after Constantine the Great's death and the end of the usurpation of Magnentius and Decentius. It is a reminder of Constantine's prophetic dream.
Constantine at at the Battle of the Milvian Bridge by Giulio Romano, between 1520 and 1524, located in the Vatican City, Apostolic Palace. Image Public Domain, via Wikimedia Commons
This coin is also a profession of orthodox Christian belief from an emperor who was an Arian Christian. It is a call for "SALVS AVG NOSTRI", "the welfare of our [singular] Augustus", Constantius II, son of Constantine. This call is a contrast with coins issued by the usurpers and brothers Magnentius and Decentius, calling for SALVS DD NN AVG ET CAES : "the welfare of our lords [plural] Augustus and Caesar".
Constantius II, AD 337-361, Æ Centenionalis (22mm, 6.45g, 12h), Treveri (Trier) mint, uncertain officina , struck AD 353.
Obv: Pearl-diademed, draped, and cuirassed bust right
Ref: Large Chi-Rho (☧) ; A ω flanking; T[...]
Ref: RIC VIII 332; LRBC 67
for comparison here is an example of the similar coin from Magnentius (not my coin, ex-Roma Numismatics eSale 72, 2020):
This coin from his brother Decentius is my coin - again with the Chi-Rho, but unusually (S and star) at the base of the Chi-Rho.
Decentius, Caesar, AD 350/1-353, Æ (23mm, 5.92 g, 7h), Lugdunum (Lyon) mint
Obv: Bareheaded and cuirassed bust right
Rev: Large Chi-Rho; A ω flanking; FSLC
Constantine's Prophetic Dream
The Chi-Rho on the reverse of this coin is a christogram formed from the first two letters of the name "Christ" (Greek: ΧΡΙΣΤΟΣ, or Χριστός) and a reminder of the Victory of Constantine over Maxentius in AD 312.
Constantine was directed in a dream to cause the heavenly sign to be delineated on the shields of his soldiers, and so to proceed to battle. He did as he had been commanded, and he marked on their shields the letter X, with a perpendicular line drawn through it and turned round thus at the top, being the cipher of CHRIST. Having this sign, his troops stood to arms. The enemies advanced, but without their emperor, and they crossed the bridge. The armies met, and fought with the utmost exertions of valour, and firmly maintained their ground. In the meantime a sedition arose at Rome, and Maxentius was reviled as one who had abandoned all concern for the safety of the commonweal; and suddenly, while he exhibited the Circensian games on the anniversary of his reign, the people cried with one voice, "Constantine cannot be overcome!" -Lactantius, XLIV
After Constantine The Great's death in 22 May 337, his three sons Constantine II, Constans, and Constantius II. Constantius II massacred his near relatives to secure succession. Julian the Apostate recounts this:
Six of my cousins and his, and my father who was his own uncle and also another uncle of both of us on the father's side, and my eldest brother, he put to death without a trial; and as for me and my other brother, he intended to put us to death but finally inflicted exile upon us; and from that exile he released me, but him he stripped of the title of Caesar just before he murdered him. But why should I "recount," as though from some tragedy, "all these unspeakable horrors?" Julian, Letter to the Athenians, 3.5
Constans battled with his brother Constantine II for control of the western empire, with Constantine II's death the result in AD 340.
In the mean time Constantine and Constans were disputing for that part of Africa which belonged to Carthage, and for Italy. Constans, who wished to surprise, his brother, concealed his enmity for three years. He took occasion, when he was in a province that was attached to himself, to send soldiers to him, on pretence of assisting him in the war against the Persians, but in reality to assassinate him by surprise. This they accordingly performed. Such was the end of Constantine. -Zosimus, Book 2
Controversial Christian Belief
Constantius and Constans ruled together in a uneasy peace for a decade before Magnentius with his brother Decentius overthrew and killed Constans. Magnentius was a pagan, but he issued coins with the Chi-Rho and "alpha" and "omega" (first and last letters of the Greek alphabet) on the reverse to express the orthodox believe of God and Christ being the same. This a statement by (pagan) Magnentius against his Arian rival Constantius II.
Here is another coin of Magnentius - a smaller denomination.
Roman Imperial, Magnentius, AD 350-353, Æ half-maiorina (?) (17-18mm, 2.81g, 5h), Lugdunum (Lyon) mint
Obv: Bareheaded and cuirassed bust right; A behind
Rev: Two Victories standing facing one another, holding wreath inscribed VOT/V/MVL/X in four lines; /SV//RPLG
Ref: uncertain; this looks official to me (not expert in late Roman) - at this weight and with legend "MVL/X" it does not appear to be catalogued in RIC - see similar heavier coin RIC VIII Lugdunum 130
Two Greek phrases - differing only by one letter (iota) express the Arian (similar) vs. Orthodox (same) beliefs about the nature of God and Christ:
ὁμοούσιον τῷ Πατρί (Same essence or being as the Father from ὁμός, homós, "same" and οὐσία, ousía, "being" or "essence" )
ὁμοIούσιον τῷ Πατρί (Similar essence or being as the Father from ὅμοιος, hómoios, "similar" and ousía, "being" or "essence").
The most common explanation for why "iota" means "only a little bit" is that the letter iota is the smallest letter in the Greek alphabet (See "A Way with Words" podcast starting at 24:10/51:42). Although it is tempting to see the origins of our English phrase "not one iota" in "same"/"similar" story of the Arian heresy, it is a good story, but not supported by evidence. (see this blog Not One Iota of Difference).
Constantine the Great was baptized by an Arian priest near his death, and Constantius also promoted Arian belief. He would not have authorized this coin for minting.
Usurping the Usurpers
Decentius was headquartered in Trier (Treveri) but was usurped by Poemenius who closed the gates of the city against Decentius in support of Constantius II.
After Proculus, Pœmenius was condemned and put to death: he who, as we have mentioned before, when the Treveri had shut their gates against Cæsar Decentius, was chosen to defend that people. -Marcellinus, XV.VI.4
This coin, which Constantine II would have objected to in it's orthodox religious meaning, was issued briefly (2-3 months) near the end of the revolt. No other mints issued this coin - it is unique to Treveri. Holt in his article cited below shares the following timelines and uses weight of the coins as an important factor in determining dates.
This coin one is one from the "Poemenius revolt issue". Magnentius and Decentius both died by suicide after suffering defeats from Constantius' armies. In early 354, Constantius demonetised the coinage of Magnentius.
Ammianus Marcellinus, The Roman History of Ammianus Marcellinus, translated by, C. D. Yonge, Bell and Sons, London, 1911.
Zosimus, New History. London: Green and Chaplin (1814). Book 2.
Holt(2006). Usurping a usurper: the revolt of Poemenius at Trier, The Numismatic Association of Australia, Volume 17 2006
Holt, W. C. (2003). Evidence of the Coinage of Poemenis' Revolt at Trier. American Journal of Numismatics (1989-), 15, 61–76.
Lactantius, On the Deaths of the Persecutors
Julian the Apostate, Letter to the Athenians (1913) Works, vol. 2, pp.245-291