Found a cartwheel penny

Some of you might know more about this coin than me,I found one of these about six months ago but it was very rough,so I just thought it was a token of some sort.Well this one I found yesterday here in Nelson and although it to is pretty hard to make out any details or writing I can see brittania on the front and someone on the reverse.A google search says they were produced way back in 1797 and 1798,all of them were dated the same,unfortunatly I can't quite make out a date,They dont appear to have a great deal of value as they were produced by the zillion.The interesting thing is how it got its name when you look at the front in the correct way and turn it over to the reverse side in the normal manner it is then upside down (hence the name),they are much bigger than a normal penny from memory 36mm in diameter and around 3mm thick a fair ol' chunk of copper.
  Also found a another two nice silver coins,one is another english sixpence (1903),the other is an Aussie sixpence (1911).Also another nice condition penny (1874).

  We both tried the local beach but that was a bit hard found a few dollars,and Noeline managed a digital watch (still going).Ran into a local Mder so had a chat and left him to his turf ......