It could also be a counterfeit George III, just one with a little thicker head. Just matching up one letter would give you a better feeling of the ID, but you will never know for sure exactly what it is.
PS: From now on forget the ruler and just state the size in MM. It's impossible to read on a screen, and even just saying something like quarter in size is as good. Plus I might as well add... posting the picture in the correct orientation makes a difference too. A while back an old copper got posted where many said it was a George III, but then someone said the correct ID of William III, and most didn't think that made sense until I rotated the picture 20 or 30 degrees. For really worn coppers where you can't read anything it's all about the shape of the profile, so definitely helps looking straight on.