This small coin is roughly the same size as a 15th century English hammered silver halfpenny. Roger Paul is the finder (unearthed on 9 October) and it’s actually an Irish penny of Edward IV, which was struck during the light cross and pellets coinage of that king.
The best reference work on coins like this one is Irish Hammered Pennies of Edward IV and Richard III by Jasper Burns. The obverse on Roger’s find has pellets by the king’s neck and the style of the head is Burns’ class F. On the reverse is a cross pattee with three pellets in each quarter and a quatrefoil in the centre. In having pellets by the neck, a class F head and a quatrefoil on the reverse this coin must have been struck at the mint situated in Dublin.
Irish pennies were struck at various mints in Ireland and they were supposed to circulate in that country. They were smaller and lighter in weight than their English counterparts. However, a very large number ended up being exported to England. This resulted in a good profit for those who were exporting them. To make them more acceptable in England some Irish pennies had characteristics found only on English coins. This coin, for example, has a quatrefoil on the reverse, which only appeared on English pennies struck for the Archbishop of York.
In Coins of Scotland, Ireland and the Islands Edward IV pennies of this type are listed as number 6365. The centres on this specimen would grade better than Fine but the legend is completely flat on both sides. It’s actually a decent example of the type and should be worth around £35 to a collector.