Medaillon - Constantinus I CONSTANTINVS AVG; Constantinople

RIC VII 1 (Constantinople) and 164 (Nicomedia); Alföldi 746; Depeyrot 20/1 (Ticinum); Calicó 5156 (Constantinople).

Note from CNG : 

This issue has raised several questions regarding not only where it was minted, when, and for what purpose, but also what denomination it might be. While two examples of this type include mint signatures for both Constantinople and Nicomedia, the lack of one on this issue has led scholars to speculate where it was struck. Cohen was the first to note the type from a specimen in Copenhagen (see RIC VII, pl. 21, 164 for its illustration), though he misdescribed the obverse as being laureate, and he assigned its date to the period following Constantine’s death, when his successors were striking the so-called “eyes to God” obverse type as memorial issues. Bruun, in RIC VII, following his own stylistic criteria, dismissed a Constantinopolitan origin and instead suggested that the piece described by Cohen belonged to Nicomedia (RIC VII 164). Apparently hedging his bets, he also catalogued the coin as an unsigned first issue of the new mint of Constantinople, although he noted that Nicomedia was the preferred mint. The question regarding the coin’s point of origin has been further confused by Depeyrot, who assigns it to Ticinum within an emission which, “rassemble plusieurs séries de monnaies qui ont dû été émises lors du donativum de 326 et du passage de Constantin à Ticinum (brings together several coin issues which were struck during the time of the donativum of 326 and the passage of Constantine to Ticinum) .” For Depeyrot, this issue was not for some distribution “comme sur les types similaires de Constantinople et de Nicomédie (as on the similar types of Constantinople and Nicomedia),” but was, in fact, an adventus scene and could not be an eastern product.
In addition to the lack of a mintmark, Constantine’s plain banded diadem and the obverse legend may offer clues. The imperial legend also undergoes a transformation as the more traditional formula, IMP C...P F AVG, of his early issues is now replaced by the more direct and authoritative CONSTANTINVS AVG (sometimes strengthened by the inclusion of the title MAX), a title which he began to employ frequently on his coins after the defeat of Maxentius in AD 312, when he became unrivalled emperor in the west. Beginning in AD 324, however, when civil war between Constantine and Licinius I re-erupted, Constantine’s issues begin to display a new imperial obverse, as the laureate bust of his coins give way to one wearing a diadem. Based on this stylistic development, AD 324 must be the terminus post quem for this issue.
The presence of the triumphal quadriga on the reverse of this, with Constantine holding a scepter clearly topped by a eagle holding a wreath (unlike that of the Copenhagen specimen), demonstrates that this coin was issued on the occasion of some triumph, and not, as Depeyrot suggested, an adventus. The specific nature of this issue may also be indicated by the coin’s weight, which comports with the weight of the old Diocletianic aureus at 60 to the Roman pound, rather than the solidus standard established by Constantine in AD 309.
The lack of a mintmark indicates either a temporary or novel facility, as the other mints already had long-standing systems of mintmarking. The new obverse portrait type and legend suggest some political rapprochment concluded to Constantine’s advantage. And the unusual, somewhat nostalgic weight standard of such an imperial predecessor as Diocletian, implies an event designed to reestablish a strong empire of the past. Given such possibilities, then, it is highly probable, if not certain, that the RIC listing as Constantinople 1 is correct and that this issue was the first struck at Constantinople following the removal of Licinius I and his son in AD 325-326.