Did you find that at birmingham ? If so I am glad I picked the Elizabeth I three farthing coin in that £5 tray it was by far the best thing in there I found it at about 11 am
It could be a 'Hand Heller' or something similar, from the German states. Not a series I know anything about. They do have the sunk in square look on one side, but the cross on the other side doesn't look the same. There could be other types though. But as I say, I know nothing about German/Holy Roman Empire medieval coinage.
It's probably a Pfennig or Heller from the German states. Bavaria , Austria etc.
The Square in the middle would of had a shield / coat of arms for the area it was struck in.