Æ21 - Valerian and Gallienus COL AVG, TR (A)

Alexandria Troas was a Roman colony — Colonia Alexandria Augusta — founded by Antigonus and refounded under Lysimachus before Augustus settled veterans there, giving it the colonial status its coins never let you forget. The city was permitted to strike bronze coinage under the joint reign of Valerian I and his son Gallienus, a pairing that lasted only until Valerian's catastrophic capture by Shapur I at the Battle of Edessa in 260 AD, the first time a reigning Roman emperor had been taken prisoner by a foreign enemy.

That defeat effectively ended this issue type. Coins attributable to the joint reign are therefore bounded by a hard historical terminus.