At first glance I assumed it was a George III Halfpenny. The portrait is that of George III complete with legend. The reverse side with the shield/coat of arms though has me confused (easy these days

). A low value George III coin should have Britannia and only the higher value silver/gold coins have the shield ( or so I thought). It is made of copper, tips the scale at 4 grams and is 25mm in diameter.
So...what is it please ? Any ideas.
Cheers Brian

Identified - moved to British Coins forum - Sap