Also the last paragraph in the article is interesting - a British numismatist says it's ridiculous to assume that because the coin showed an emperor Sponsian that he must have existed. Any thoughts on that?
We simply don't know what happened to Sponsianus - last week we didn't even know he existed! But I think it's really important we talk about how we refer to him - headlines have been calling him a "lost emperor", but we have to remember that he never ruled the "Roman Empire" as it is popularly understood.
During the 240s CE the empire was in disarray, under Emperor Phillip the Arab many of the far-flung provinces were being lost or cut off. One of these was Dacia, in modern Transylvania (and Oltenia and Banat), a remote outpost of the Empire surrounded by enemies. Dacia was not lost until the 270s, under Emperor Aurelian, but during Phillip the Arab's time it was temporarily cut off from Rome.
With a population of several thousand Romans and potentially up to a million Romanised (to a lesser or greater extent... Some were loyal Romans, se were in open rebellion, we'll probably never know the statistics) Dacians being cut off like this was terrifying. With the power of Rome lost, Sponsianus was able to declare himself emperor - but only of Dacia. He never ruled outside that area.
We simply don't know what happened to him when the lost province was reconnected. He might have already been dead. Either way, by 275 the Romans had evacuated their military and administrative assets for redeployment.
What's very interesting though is that we're already seeing the fight for Sponsianus's reputation. The researchers who proved his existence have been keen to label him a reluctant ruler stepping up when Rome failed, others have called him a usurper. Without any more substantial evidence than two coins, we'll almost certainly never know much more than we do now.
It is several days later, but I want to chime in with a skeptical response for why we should take Pearsons claims with several grains of salt.
A disclaimer at the start: I am not an expert in Roman coins, nor even a specialist on Roman empire. However, the information that follows is the close-paraphrasing of arguments of the numismatist Marjanko Pilekic and of Roman historian and coin specialist Johannes Wienand. (both of these threads h/t /u/enclavedmicrostate )
Let's start off listing reasons why these experts, and a 200 year long lineage of numismatists before them, think these coins are forgeries.
The Romans never made gold or silver coins by casting, gold and silver were always struck. If these coins were genuinely of Roman manufacture, they would be the only known examples of cast gold roman coins.
From what I have read, some Roman coins of Bronze and copper were cast, though it seems these were produced in the 3rd century BC or earlier.
On the other hand, it was extremely common for early-modern forgers in the 18th century (when these coins enter the historical record) to make their coins through casting.
It would be exceedingly unusual for a genuine coin produced in the 3rd century AD to revive a design from 400 years earlier, not least because 400 year old coins are not usually still in circulation.
If you look at the coins of other emperors from the same time period, between 235-280, they ALL bear legends that wrap around the portrait, from 7 o'clock to 5 o'clock. For example Gordian II, Philip the Arab, Aemilian, and Gallienus. There was a very standard layout for imperial coinage, and once again the Sponsian coin, if genuine, would be a dramatic innovation away from that standard.
Also, the legend reads 'Imp Sponsiani" in the genitive case. Literally "Imperator of Sponsian" rather than the standard nominative case. The other coins listed all give the nominative case, Phillipus, Aemilianus, Gallienus, etc. Numismatists have thought that this weird use of the genitive case is because a forger that did not read Latin made a mistake.
The results they found are here
All others had negligible copper content. However, the Sponsian coin was 93% gold, 3.5% silver and 3.5% copper. Again, this is very weird, and raises the question of where was the source of the gold that went into this coin? If the copper composition is significantly higher than other associated coins, does that mean the gold was mined in Dacia? Outside the Roman empire?
Also, Johannes Wienand notes that the weight of the Sponsian coin is 10 grams, which is slightly off of the normal weight of a double-Aureus of the period. From some quick googling, the weight of Aureus in the period circa 240-250 were ~3.5 grams. I assume a double-Aureus would weigh ~7 grams (though I could be wrong).
Now, there is also the example of Domitian II, where there was no written mention of Domitian II as an emperor and only one coin was found in France in 1900. So, historicity of Domitian II was debated until a second coin was found in England in 2003 and a third found in Bulgaria in 2006.
Domitian II is now considered a genuine figure, and he is conventionally dated to circa 270 AD.
Now, I want to consider two points that Pearson and his co-authors emphasize as "smoking gun" evidence that the coins are authentic.
First, Pearson points to small scratches on the surface of the coin as evidence the coin was in circulation, banging against other coins in a purse for years. Pearson claims that no other source could produce such distinctive scratches.
However, I hear a lot of skepticism from numismatists on that claim. Alfred Deahl points out that Carl Wilhelm Becker was known to put his coins in bags of grease and iron filings to give a worn look and a fake patina.
Also, coins in circulation do not wear at an even rate. There is not any way to know if a coin has been in circulation for weeks and seen tough use, versus many years of light use.
Secondly, Pearson points to minerals and trace amounts of sulphur crystals on the surface of the Glasgow Sponsian coin as consistent with coins that have been buried underground for hundreds of years.
However, as I already said the Sponsian coin was first recorded in 1713, and Pearson provides a chart to track ownership of the coins. Over the 300 year recorded history of this particular coin, there is ample opportunity that the surface of the Sponsian coin may have been contaminated by long contact with genuine ancient coins.
Finally, I want to say that there are 3 possibilities here.
Possibility 1, which Pearson et al propose, is that a person named Sponsian claimed imperial title and had these coins made circa 270 AD. Pearson et al claim the many irregularities of the coin come from minting coins in backwater Dacia using local craftsmen because more standard craftsmen and equipment was inaccessible. They present evidence which they say proves the coin dates to this period, and it is thus genuine and Sponsian is thus real.
Position 2 has been the Numismatist consensus from the mid 1800s, that these coins are forgeries made some time soon before 1713. A skeptical reading of Pearson et als results would dispute that he even proved the coins are ancient, rather than being contaminated.
Position 3 is that these coins genuinely are from the 3rd century, but are ancient counterfeits. Ancient counterfeits did happen, and counterfeiting workshops in 1st century Poland have been found. If these coins were fakes made in Poland or Ukraine in the 3rd century, that would explain some of the weirdness of the coin, like the "Sponsiani" inscription. It is harder to explain why a fake coin would be made out of gold, and still does not explain why the Republican era reverse design appears in 3rd century.
Both Pilekic and Wienand seem to leave the door open to this third possibility, that it is an ancient coin not made by an imperial claimant.
I think that this possibly explains your question:
a British numismatist says it's ridiculous to assume that because the coin showed an emperor Sponsian that he must have existed.
If the coin is either modern fake or an ancient fake, which we know exist, then the existence of Sponsian is back in doubt. Pearson only really presents evidence that the coin is old, and can only conjecture why it might be authentic.
edit- many typos.
