NOT IN RIC
UNLISTED ISSUE. DRC apparently mentions this issue in the article "LIBERATOR ORBIS": "-The Liberator of the World.-This new title, and sufficiently assumptive, appears on a third brass of Constantine the Great, the type which it accompanies being that of the emperor on horseback with his right hand raised, and a lion crouching under his horse's feet. -Eckhel refers it to the successes of Constantine over either his rivals or the barbarians whose incursions were pernicious to the whole Roman world, and who therefore on this medal are shadowed forth under the image of a lion trampled upon by a horseman" (p. 517).
Maurice lists this type for Constantine I (all four officinae) and Licinius I (only officina S, bust type B4). See: J. Maurice, Numismatique constantinienne, vol. I, Paris 1908, p. 215; one example on plate XVIII, no. 4.
In RBC listed under no. 234CI for Constantine I only (see p. 31 and plate 14). Failmezger describes this type as "Emperor riding down lion", giving it the highest rarity (RR) and adding to the group of "the special victory coins struck after the battle of the Milvian Bridge by Constantine to celebrate both his defeat of Maxentius and to show solidarity among the three remaining emperors" (p. 31).
The time of issue was probably the year 315 when Constantine arrived to Rome to celebrate his decennalia. At the same time the great triumphal arch was finished, dedicated to Constantine as LIBERATORI VRBIS. Cohen lists this type not only for Constantine (Cohen, vol. VII, p. 265, no. 317), but also for Licinius (Ibid., p. 201-202, no. 132-133): with R*S or RS (Rome) and ALE (Alexandria) in exergue. Kent follows Cohen in listing LIBERATOR ORBIS type for the both Augusti, Constantine and Licinius, but he identifies it as minted exclusively at Rome in 312-313 (see Kent, p. 50, no. 454-455).
Also listed, for Licinius only, in: Meixner, I., "Neki kovovi iz nalaza kod Stoca koje ne poznaje najnovija radnja Sutherlanda »Roman Imperial Coinage«, VI sv. 1967. godine" [Some coins from Stoca hoard which are unlisted in the latest Sutherland's work "Roman Imperial Coinage" vol. VI, 1967], Numizmatičke vijesti, vol. XVI/27, 1969, p. 16-18 and plate V.
Finally, Jean-Marc Doyen attested in his article ("Une émission constantinienne méconnue (Rome, 313) et la date de la 3ème réduction pondérale du follis", Bulletin du Cercle d'Études Numismatiques 1990, no. 1, pp. 1-9) four officinae for Constantine I (bust B4) and three officinae for Licinius I (S, T, Q; bust type B5).
Note that there are two variants of reverse: with or without shield on left arm. It is uncertain if this difference constitutes two separate issues. Emperor is probably always laureate (but Cohen gives "Licinius casqué" for no. 132). He has right hand raised and empty, but, surprisingly, on many specimens tip of a spear is visible near the lion's head.
Should be listed after ROME 17.
ROME [after 17], CONSTANTINE I, UNLISTED ISSUE, OFFICINA P
ROME [after 17], CONSTANTINE I, UNLISTED ISSUE, OFFICINA S
ROME [after 17], CONSTANTINE I, UNLISTED ISSUE, OFFICINA T
ROME [after 17], CONSTANTINE I, UNLISTED ISSUE, OFFICINA Q
ROME [after 17], LICINIUS I, UNLISTED ISSUE, BUST TYPE B5, OFFICINA P
ROME [after 17], LICINIUS I, UNLISTED ISSUE, BUST TYPE B5, OFFICINA S
ROME [after 17], LICINIUS I, UNLISTED ISSUE, BUST TYPE B5, OFFICINA T
ROME [after 17], LICINIUS I, UNLISTED ISSUE, BUST TYPE B5, OFFICINA Q
ROME [after 17], LICINIUS I, UNLISTED ISSUE, BUST TYPE B5