Here goes:
1. The legend is EDW R' ANGL' DNS HYB. If there is no A after the EDW and only one R then it is always Edward I.
2. The crown has the trifoliate side fleurs (see
http://www.detectingwales.com/index.php?topic=3648.0 for explanation. The trifoliate fleurs generally mean Edward I Classes 1-9
3. The letters E and C are open, usually meaning Classes 1 to 5, although there are a few exceptions.
4. The letter S is of an early type where each letter is made up of 4 separate wedge-shaped punches rather than one whole letter. This identifies it as being Class 1-3e, some 3g or some Class 7.
5. The mint is Canterbury (CIVITAS CANTOR), which issued pennies in all classes EXCEPT 1, 3a, 3e, 6a and 8.
So far, then, it could be Class 2a, 2b, 3b, 3cd, or 3g.
6.The ornaments on the crown are spear-shaped rather than round. This excludes Class 3b.
7.The letter Ns are the right way round. This excludes most of Classes 2a and 2b
So we are left with Class 3cd (which used to be separated into 3c and 3d but are now lumped together) or 3g. Most Class 3g have down-curving outer fleurs, which I think are not present on this coin, so my final conclusion is that this coin is Edward I, Class 3cd
Anyone up for another?