How to Identify the Antoninianus of Gallienus

Start with the crown, because it defines the denomination. An antoninianus carries a radiate crown, a ring of pointed sun-ray spikes around the head, whereas a denarius of the same era shows a plain laurel wreath. If the male portrait wears radiate spikes, you are looking at an antoninianus rather than a denarius. Confirm the ruler by reading the Latin legend that runs around the obverse rim, since many third-century emperors struck near-identical radiate coins and only the legend names Gallienus.

Check the fabric and size next. These are billon coins, a debased silver-copper alloy, typically about 18-22 mm across and only a few grams in weight. Surfaces most often read coppery or grayish-brown, sometimes with patches of surviving silvery wash; a warm bronze look is normal and does not mean the coin is a fake or a different denomination. A coin that is much larger and heavier, or plain copper without any radiate crown, is likely a different denomination or a later radiate imitation.

Work through the reverse. Gallienus used a very wide range of reverse types, mostly standing deities and personified virtues holding attributes such as a scepter, patera, cornucopia, spear, or globe, each named by its surrounding legend. Identify the figure from both attributes and legend rather than guessing from the pose alone. Later in the reign, look in the exergue beneath the figure for a mint or officina mark, a letter or short group of letters that helps attribute the coin to a specific workshop and mint.

Watch for look-alikes. Radiate coins of other third-century emperors, of the empress Salonina, and of the breakaway Gallic and Palmyrene rulers share the same fabric and style, so the obverse legend is essential. Small, crude "barbarous radiates" copying coins of this era circulate widely and are lighter and cruder in style. Modern cast forgeries exist as well; these tend to show soft, blurry detail, grainy surfaces, and sometimes a faint seam around the edge.

Authenticate by fabric and strike. Genuine antoniniani are hand-struck, so expect slightly irregular flans, off-center strikes, and lettering that is sharp but not perfectly even. Because these coins are common and inexpensive, high-value forgeries are less of a concern than with gold, but for a notable or scarce reverse type it is still worth comparing against published references or asking a specialist ancient-coin dealer.