Not a Seal, Lead Bullet After Impact, Image by StuE, Found by Adam & Lisa.
Found in Suffolk, 14.5 x 20.5 x 9.7mm, 10.3g.
Probably a 9mm bullet which has taken on an imprint of the surface it struck. The tail of the slug is still largely intact and recognisable. Occasionally the entire bullet will be flattened making it even more like a seal.