Georgius 3rd Coin 'Hibernia' 1805/6?

I have a coin with Georgius III D.G.REX on front and 'hibernia' and a harp on the back, the date is the only slightly worn bit, and says either 1805 or 1806, (its just the last digit that is a little hard to distinguish) the rest is very clear although circulated, Does anyone know anything about it, and what it may be worth, if anything,