Nicopolis ad Isthmon was a minor Achaean mint that produced provincial bronzes sporadically under the joint reign, and issues naming both Valerian and Gallienus together as co-emperors bracket the period between Valerian's accession in 253 and his capture by Shapur I at the Battle of Edessa in 260 — the only time a reigning Roman emperor was taken prisoner by a foreign enemy. After that humiliation, Gallienus ruled alone, and coins naming the pair ceased.
Nicopolis ad Isthmon was a minor Achaean mint that produced provincial bronzes sporadically under the joint reign, and issues naming both Valerian and Gallienus together as co-emperors bracket the period between Valerian's accession in 253 and his capture by Shapur I at the Battle of Edessa in 260 — the only time a reigning Roman emperor was taken prisoner by a foreign enemy. After that humiliation, Gallienus ruled alone, and coins naming the pair ceased.