Thailand coin dating
So while it would be useful to be able to date the coins from Katsuren Castle more precisely, they do not necessarily indicate even indirect links between east Asia and Rome in the mid-4th century (although such indirect links are not altogether impossible).
There are plenty of Roman coins in southern India and Sri Lanka that are evidence of direct links with the Roman world, and direct trade with these areas is not in doubt.
A few Roman coins, and imitations of them, have been found in China, where they were probably used as ornaments and as burial goods.
Yet these too are usually made of gold – and most are later in date (5th to 7th centuries).
However, they imitate Roman gold coins of the first and second centuries – and none resembles any of the coins from Katsuren Castle.
The Roman coins are not so easy to identify from the obverses alone.
The coin that features most frequently in the news reports appears to be a copper alloy coin of Constantius II (337-361AD), the son of Constantine the Great.
Archaeological evidence from the Isthmus of Kra on the Thai peninsula includes imported materials from Han China and the Roman empire, though these could have arrived indirectly through India.
Gold pendants copying Roman gold coins were used in ancient Thailand and Vietnam, and a stone mould for casting such objects has been found in southern Thailand.