At various times in the Roman Empire coinage fell into short supply. This tended to either be in periods of rapid expansion, or of great upheaval. This coin is from the latter.
Ugh. Not much to look at. It is of a type sometimes called a "Barbarous Radiate". Numismatists do not fully understand these coins. They were churned out in large numbers during the Third Century AD, especially in mints located in Gaul and Britain. The extreme variability of style, and the general lack of artistry, makes it seem as if the equivalent of village blacksmiths went into the money making business across the Western provinces of the Empire.
This was a time of major economic and social unrest. Perhaps the machinery of government just broke down to the point where not even the most basic functions could be managed. Commerce had declined and partly reverted to barter. Suspicious consumers would probably "trust" older gold and silver coins but there was still a need for what we would consider small change. Absent any authority to either encourage or to ban the practice, people just made their own "pennies" in whatever form would be accepted on a local level.
Of course the "official" coinage had long been declining in artistry and precious metal content so it is not always easy to tell just how crude a coin would have to be to qualify as "Barbarous".
This one probably does. Crummy metal, hence the bits missing. The blank on which the coin was struck (a "flan" if you want to be a smartypants) is undersized, the lettering spills over the edge. The reverse shows a seated goddess holding a peculiar amalgam of cornucopia and a star with some kind of orbs around it.
If it was not "official" coinage it probably does not matter, but I suspect the coin was based on an original of Claudius Gothicus who reigned for two years only, 268-270 before he died of plague. Like so many other aspects of "Barbarous" coinage nobody is quite sure why the coinage of Claudius and his predecessors Tetricus I and II were the most common Emperors copied unofficially.
This "might" be the original from which the above coin was derived. Overall similar layout but whoever cut the die on my coin seems to have gone overboard with the star and cornucopia details. And is the goddess figure seated or standing in my example?
Next time a few more "Barbarous" coins......