This is a bronze Nummus coin of Constantius I who was Roman Emperor between AD300-303.
Look closely and you can read his name CONSTANTIVS in capitals around the top.
We can tell he is Emperor because he is wearing a laurel wreath around his head.
It is one of several Roman coins found by archaeologists at Folkestone Roman Villa.
The coins that have been found show that the villa was occupied for most of the Roman period (AD50-395). But no coins have been found dating between AD 275-296, so it appears it was completely abandoned at this time, although it was occupied again during the 4th century.
Other coin finds at the villa include
a copper alloy As of the Emperor Claudius I, who was Emperor when the Romans conquered Britain in AD 43;
a copper alloy As of the Empress Faustina II (AD 161 -175);
a silver Denarius of the Emperor Elagabalus minted in AD 221.
Folkestone Museum has an excellent collection of Roman coins. Coins are important because the pictures on them can tell us a lot about life in Roman times including fashions hairstyles, gods and goddesses, ships, warfare, gladiators and a lot else besides.