I just received this coin in the mail from the Frank Robinson auction. Gallienus was an emperor who had to appeal to the loyalty of the army, like many others before him. The problem was, the empire started to crumble in the years between 253 and 260 when he held joint power with his father Valerian I. I've found it interesting to focus on coins of his that were struck within this period because of the better workmanship, quality of metal, and superior aesthetics when compared with the mass quantities of billon antoniniani issued between 260 and 268 during his sole reign. Interestingly, one can acquire sestertii from this period when the relationship between the bronze and silver still made economic sense to his subjects, whereas after 260 and the discontinuance of the sestertius and abandonment of silver coins no one knows the relative value between the base metal antoniniani and the gold aureus, which still was produced during his sole reign, a question that numismatists and economists alike could ponder endlessly. The aureus fell from around 4.0 grams at the start of his reign to as little as 2.5 grams during its second half. If one searches a bit, good quality portraiture, which had characterized the orichalcum sestertius for over 250 years, can still be found. In that spirit, I offer this example: Gallienus (253-268) AE Sestertius 28 mm 14.8 grams, squared flan, struck between 253 and 260. Obverse: Laureate, draped, and cuirassed bust right, with the legend IMP C P LIC GALLIENVS P F AVG Reverse: Fides standing left, holding two standards, with the legend FIDES MILITVM, S C in field Reference: RIC 214, Cohen 240, Göbl 74s Feel free to share your Gallienus sestertii, or any of his coins!
I can offer one of the poor-quality billon antoniniani.. Gallienus Antoninianus, 259 Samosata. Billon, 22mm, 2.62g. IMP C P LIC GALLIENVS P F AVG. VIRTVS AVG, emperor holding spear, receiving wreath from Roma holding spear and shield (RIC V.1 (joint reign) 457 var). Reportedly from a hoard found in Bristol, England in 1997.
I think you're right that the dual-reign portraiture tends to be a lot better. Your sestertius is a great example! Here's a sole-reign Gallienus I bought for its nice-style portrait:
Gallienus antoniniani with animal reverses, mostly from the Zoo Series. The portraits are of varying quality! Bull (Legionary Series) Lion (Antioch) Centaur Gryphon Antelope Doe Gazelle Tigress Detail showing stripes: Pegasus