How do I identify a UK Edward 111

Hello all. I have just joined, and being new to coin collecting, am entirely dependant on those with a far greater knowledge than I. So a basic level question please. How do I identify a UK Edward 111 groat please. I have not a clue what I should be looking for, and am interested in buying one that I have seen. Thank you in adavance.

Reference books are:
North, J. J. 1963. English Hammered Coinage
Skingley, Philip. 2007. Coins of England and the United Kingdom
The Numismatic Chronicle and Journal of the Royal Numismatic Society

There is a good site run by Tony Clayton ...
http://www.coins-of-the-uk.co.uk/pics/hamm/ed3/4d/index.html