Image source: Promptuarii iconum insigniorum, AD 1553
I've been looking for this coin for about a year (since April/May 2020) to complement several others that can be seen in my post about Gallienus and usurpers. My coin of interest: an Alexandrian Tetradrachm from Gallienus' regnal year (RY) 8. RY 8 is a bit of a challenge to find because the usurper Macrianus and his two sons controlled the mint for most of the year. Macrianus Major and his two sons Macrianus Minor and Quietus fought in the Roman army under Valerian when he was captured by Shapur I (AD 258-259). After the capture of Valerian, Macrianus and Ballista (aka Callistus) attacked Shapur causing him to retreat beyond the Euphrates River. Macrfianus was acclaimed by his soldiers as emperor, however, as he was lame and old, instead proclaimed his sons Macrianus Minor and Quietus as joint emperors.
The mint at Alexandria started minting coins in the name of the usurpers in September 260. However, before the end of August 261 it was issuing coins in the name of Gallienus. A paper by Legutko (2002) outlines evidence related to the minting of coins by Macrianus in 260/1 and includes other interesting observations related to the coins of Gallienus from Alexandria after 260. Here are the coins of the two usurpers:
Egypt, Alexandria, Macrianus, Usurper, AD 260-261, BI Tetradrachm , Dated RY 1 (260/1 AD); September 260-May 261 AD Obv: AK T Φ IOΥN MAKΡIANOC E CEB Laureate and cuirassed bust right Rev: Eagle standing left, wreath in beak; LA (date) in left field Ref: Dattari 5380 plate 275 Obv Latin Equivalent: IMP Titus Fulvius Junius Macrianus E AVG
Egypt, Alexandria, Quietus, Usurper, AD 260-261, Tetradrachm dated RY 1 (circa September 260-May 261 AD) Obv: A K T Φ IOVN KOVHTOC Є CЄB, laureate, draped, and cuirassed bust right Rev: Eagle standing left, wings open, wreath in its beak; L A (date) to lower left Ref: Dattari (Savio) 5382 "the much-discussed papyrus POxy 1411 discusses the refusal of bankers to accept τό θείόν των σεβασιών νόμίσμα, 'the sacred coin of the emperors', referring to Macrianus and Quietus, and is dated to Hathyr 28 (25 November 260). Why the bankers did not accept the coins is unclear. They may have objected to the weight standard of the new coins, which average about a quarter of a gram lighter than those of Valerian's year 7 (29 August 259-28 August 260)." -LEGUTKO, P. (2002). The Revolt of Macrianus and Quietus and its effect on Alexandrian Coinage, AD 260-263. The Numismatic Chronicle (1966-), 162, 135-168.
Finally - here is the coin from the end of Regnal Year 8:
Egypt, Alexandria, Gallienus, 253-268 AD, BI Tetradrachm (23mm, 9.66g). Dated RY 8 (circa May- August 261 AD) Obv: AVT K Π ΛΙΚ ΓAΛΛIHNOC CEB, laureate and cuirassed bust right Rev: Eagle standing left, holding wreath in beak; LH (date) to left Ref: Dattari (Savio) 5290, Emmett 3803 This coin from the Rhakotis Collection, an impressive assemblage of Ptolemaic and Roman Alexandrian coins formed in the 1960s and 1970s. "Rhakotis" means 'construction site' in ancient Egyptian, a rather prosaic name for the newly founded Greek city of Alexandria.
In the Autumn of 261, the Macriani, father and son, traveled west to take on Gallienus and were defeated by Aureolus or Domitianus in Illyricum. Quietus stayed in the east to secure the region, and failed as Odaenathus of Palmyra gained power in the region. Quietus was killed in Emesa. This was not the end of unrest in Alexandria as the prefect Aemilianus was next to take the role of "usurper".
References in addition to those linked above
The Alexandrian Coinage of the Eighth Year of Gallienus, J. G. Milne, pp. 152-161, 1917 in Ancient Egypt vol. 4 by Peter Flinders, MacMillan and Company.
Milne, J. G. (1918). The Shops of the Roman Mint of Alexandria. The Journal of Roman Studies, 8, 154–178.