I have no experience in collecting ancient coins. I recently bought a coin from an Ebay auction for $1.25, shipping included. When I received the coin it was different than the one I bid on although the description stated I would receive the coin in the picture. The coin I received has much better details and readable legends. So, because of the source of the coin, the price and the switch for an apparently better coin, I have every reason to suspect it is fake. It has been a great experience for me. I have learned a lot about Roman coins and have spent several hours researching. I definitely got my dollar's worth of entertainment. I believe this coin to be a Gallienus or at least a Gallienus fake. I would describe the obverse as being a radiate head, cuirassed bust with the legend saying, "IMP GALLIENUS AVG". The reverse has the emperor on the left with a scepter receiving a wreath from Victory. I am not too sure about the reverse legend; "VICTORIA" is clear and I think the second word is "GERMAN". It is just shy of 21 mm in diameter and weighs 2.8 g. From what I have found, there were duplicate varieties of this type of coin. I didn't find any with a similar weight to this coin. The tip of the scepter is in an odd location, between the C and T. There is a die crack on the reverse. I don't see any bubbling on the surface but there is lots of pitting on the obverse which may be corrosion. I believe there are flow marks especially around AVG. I don't see a seam or filing on the edge, but there is a particular spot with extra metal.
These coins of Gallienus were struck by the millions and they were of debased metal, of poor workmanship and, with the exception of his "zoo" series and legionary series, in low demand. They are quite literally the type of coin people buy in bulk lots for a dollar or two per coin. Because each one was struck from hand-engraved dies, variations in the devices such as scepter placement with regard to the lettering of the inscriptions is to be expected and is meaningless. There's no reason to suspect this is fake.
I think it is authentic. There is no reason to fake a coin like the one you received. True, your coin is worth more than the $1.25 that you paid for it, but not a lot more, certainly not more than $5 or so. I imagine the dealer just sent you the wrong coin by mistake. The person who received your coin probably complained to the dealer, and the dealer just refunded his money. I also think you did some great research to figure out the emperor and type. Congratulations on your sleuthing skills. Are you hooked on ancients yet?
These coins are amongst the most commonly issued and found and not likely to be faked for that reason. As a first ancient you actually did well and your attribution is quite good. I have collected all kinds of coins of coins my whole life ( a pretty long one, thus far) and of all of them it is the ancients that I most enjoy collecting. You will find a fair amount written on your emperor. I have always felt sorry for the poor guy. The bottom dropped out of the empire at the start of his reign. His father, the emperor Valerian, was captured in battle and died beneath the heel (literally) of his Persian captor, a good portion of the Empire seceded from the government of Gallienus but despite that he still tried to recover the dissident provinces and for his dogged efforts and good work, he was assassinated. You will not find many "Happy Days Are Here Again" reverses on his coins.
That's not one of the most common reverse types. The quality and color of the metal makes it appear to be from the early or joint-reign era, before Valerian's misadventures in Persia. Soon after he assumed the sole imperium, the Empire's fiscal situation had deteriorated to a point that to keep up with the rampant inflation, the silver content of the (already mere billon) antoninianus dropped to near zero - and all the way to zero in some places and cases. It was during Gallienus' sole reign that the "official" practice of silvering - applying or creating by various processes, a thin film of silver, or at least a white-colored metal over the copper - was adopted by the administration as an acceptable technique at many of the mints. This was not without exception and the coinage of Antioch, particularly, tended to be of a better quality of metal (relatively speaking) and the workmanship of higher standards than at many of the other mints. The presence of a pontil - the place(s) on the rim where the cast blank was broken off from the "tree" of flans in which it was cast - is very common on ancient coins of almost all types and not, by itself, a definitive indicator of inauthenticity. Looking quickly in RIC V, your coin seems most likely to be RIC V, i 452. The "RIC frequency" rating is "scarce". It would also be RSC 1173.
The postage / S&H on such a purchase, alone, would have been a steal for $1.25, not even including the coin - you could probably say you made a net profit on that transaction.
Great adventure into ancient coins and had a lot of fun. Sleuthing skills are all part of numismatics whether ancients or modern coinage. Cheers.