It would be useful to contact the British Museum's Numismatic Department. You'll find them very helpful but try to get better photographs to send them.
http://omnicoin.com/coins/905223.jpg
Not sure of the class but here's a Celtic Potin circ. 150 BC, that either was run over by a plough or the minter had a bad day !
I don't know if I'm premature but here's an entry for Class A1. It's a Celtic Potin and I can't decide whether it's years underground or just poor workmanship !!!
http://omnicoin.com/coins/905223.jpg