The third century was a complicated and difficult period in the history the Roman Empire.

By the middle of the third century the Empire had split into three smaller empires: the Central, the Gallic and the Eastern Empire. Across the century there were lots of emperors, and ruling one of the empires could be tricky – there was always the chance you would be usurped!

The Hoard The Plompton Hoard, a collection of over 600 coins found near Knaresborough in North Yorkshire, presents a picture of this troubled period in Roman history. The hoard was found by a metal detectorist during the 1990s – the coins were scattered over a concentrated area in two main groups: over 280 coins were initially found in 1990, followed by another 270 coins over a three year period. The finder generously donated all the coins to the museum, and when another 50 coins from the hoard were found in 2013, these joined the rest at the Yorkshire Museum.

The coins of the Plompton Hoard are all from the Central and Gallic Empires, issued c. 253 – c. 282AD. The hoard is composed of radiates, a type of silver coinage which came to dominate the currency of the Roman Empire in the third century. The coins are called ‘radiates’ after the type of crown the emperors are wearing.

Radiates

Lots of radiate coinage was produced during the third century, though the value of each coin was quite low. This is because the silver content in radiates dropped over the century from c. 20% silver in each coin to as little as 3% – this saw the number of coins minted increase dramatically as the value of each coin continued to fall. Given the political instability in this period there was also a need to mint more coins to pay the soldiers who were defending the empire – the number of mints producing these coins also increased to meet demand.

The quality of the coins is not always very good – this is because, given the low silver content the coins are mostly made of base metals like, copper, which means that they are more likely to corrode when left in the ground. Some coins are so badly corroded we cannot tell what they are – we call them ‘illegible radiates’ because we cannot read the writing on them.

The Central Empire

While there were over twenty emperors proclaimed in the Central Empire during the third century, in the Plompton Hoard we only have coins from seven emperors. This is because not all emperors were around long enough to issue coins in their name, and some coins from short reigns did not reach Britain.

In the Plompton Hoard we have coins from Valerian, Gallienus, Claudius II Gothicus, Quintillus, Aurelian, Tacitus and Probus. We also have two coins which were minted for Gallienus’ wife, Salonina.

Salonina’s coins are not uncommon for the period, other imperial wives between the second and fourth century had coins minted in their names. Salonina does not wear a radiate crown, she wears a diadem instead. On the reverse the goddess Juno holds a sceptre.

Emperor Aurelian is perhaps more famous for the walls he built around Rome than for his coins, however he did try to improve the coins being produced in the Central Empire. By 274 he had increased the silver content to 5% – you can tell these coins from his earlier issues because they are marked with XXI, or on Greek coins KA, indicating that they are 20 parts copper to one part silver. There are two Aurelian radiates in the Plompton Hoard, but they are both unreformed.

This general improvement in the coinage continued after Aurelian died. Although Tacitus only ruled the Central Empire for six months he did issue coinage. We have four coins minted in his name, one of which shows the figure of Pax or ‘Peace’ on the reverse. The obverse, or face of the coin, is one of the best preserved from the hoard.

The Gallic Empire

In the Gallic Empire there were fewer emperors, but they still have seven in only 14 years! Postumus was the most successful Gallic emperor, staying in power for 9 years. Coins minted during Postumus’ reign maintained a higher level of silver than in the Central Empire – between 260 and 268 most radiates minted in the Gallic Empire had c. 15% silver, while in the Central Empire it was as low as 6%.

The higher levels of silver in Postumus’ coins has meant that some have been quite well preserved, this coin of Postumus found within the hoard shows Sol, the Sun God, on the reverse, with his cloak fanning out behind him.

The most common type of coin found in Britain from the Gallic Empire are radiates produced by Tetricus I. He was emperor from 271 to 274, and in 272 he named his son, Tetricus II, a Caesar as well, so that they could rule the Gallic Empire together. The coins minted by Tetricus I are very poor quality, with as little as 1% of silver in each coin. The low levels of silver meant that more coins needed to be produced, and there might have been as many as 1 million radiates produced every day during Tetricus’ reign!

The quality of Tetricus’ coins was generally poor, however, and they have suffered badly from corrosion on account of the low levels of silver found in each coin.

What does the hoard tell us?

Fewer documentary sources have survived from the third-century to tell us about life across the Roman Empire. It was a period of rapid reigns and regular usurpations, meaning that not all emperors received much attention in written accounts of the period. Coins are therefore a great way to learn about the different emperors that reigned across the third-century.

The Plompton Hoard was deposited at an interesting time for the Roman Empire as a whole. The hoard was buried before two significant developments for Britain and for Roman coinage.

The first was that in 286, only a few years after the last dated coin in the hoard was minted, a break-away empire emerged in Britain: the Brittanic Empire. This meant that for nearly seven years Britain was no longer part of the Gallic Empire, but was ruled separately. Although the Brittanic emperors minted coins, like Carausius and Allectus, none of their coins have been found in the hoard. This means that the coins were buried before the Brittanic Emperors started minting coins.

The second change was that at the end of the third century there were a series of reforms which improved the coins produced across the Roman Empire. The Diocletian Reforms returned the Roman economy to a three-metal system, with coins in gold, silver and base metals like copper. The radiate coinage, which had dominated the third-century economy, was replaced – the silver denarius returned to circulation.

So, why was the hoard buried? We don’t really know for sure, but someone may have just buried the coins for safe keeping. Alternatively, the owner may have felt under threat on account of the unstable political situation and so buried the coins in the hope of collecting them later on.

Why did the owner not recover the coins? It is possible that the owner was not able to return and recover the coins. It is also possible that, when the coinage was reformed, they realised their hoard had little value in the new system and so did not bother to dig the coins up. However, it is always possible they just forgot where they had buried them!