Joannes on a solidus.
wikipediaOn the death of the Emperor Honorius (15 August 423), Theodosius II, the remaining ruler of the House of Theodosius, hesitated in announcing his uncle's death. In the interregnum, Honorius's patrician at the time of his death, Castinus, elevated Joannes as emperor.
Ioannes, (Latin: Iohannes Augustus) known in English as Joannes or even John, was a Roman usurper (423–425) against Valentinian III.