Whilst walking at low tide at Brancaster Beach in North West Norfolk, I stood on a dozen of these shells. It took a while to find out that the mixture of 20 mm and .50 cal machine gun shells, dated 1941 to 1944, were almost certainly fired from the combined guns of a Supermarine Spitfire. Perhaps in the Battle of Britain or, more likely, firing on the SS Vina, a target practice ship whose remains can still be seen at extreme low tide. Not the usual shells on the beach.