Not a Seal, Pot Mend, Image by StuE Found by Colin Gilbert.
Found on the Essex / Suffolk border.
Often confused with lead seals a pot mend is a lump of lead that has been used to mend a hole in a pottery, wooden, leather or iron bucket / container to render it reasonably water tight again. When the material rots away the led plug is left with its distinctive groove that often shows traces of the original container or it's decay products.
