This coin was sent in by Anthony Hopkinson but was found by a detecting colleague. It was thought to be a Roman siliqua but I was asked to provide more details.
Firstly, this is a silver siliqua of Arcadius, whose dates are AD 383-408. On the obverse there is the laureate, draped and cuirassed bust of the emperor and a legend reading D N ARCADIVS P F AVG.
On the reverse the seated figure of Roma holds the tiny figure of Victory (resting on a globe) and a spear and is accompanied by a legend reading VIRTVS ROMANORVM. The mint letters, situated in the exergue (TR PS), are those for Trier.
The coin is slightly short of flan but the details are all clear and overall it would grade good Fine. In its present condition it should be worth £50 – £60.