It's either an Elizabeth I Halfgroat or Penny of the Second Issue with m.m. Cross Crosslet. I would be inclined to say Penny but it's hard to tell as many coins were clipped therefore altering the diameter. It is London mint, if you look around the shield, starting after the m.m., it reads CIVI TAS LON DON = City of London. A neat little coin! Kindest Regards, Clive.