I need help identifying this relic item I bought at Malvern this weekend it is supposedly the lid off of a Royal Navy charge container

[Mister militaria]

The information I have is says that it is a British Naval Charge container for no36 charge dated 1940 used by large naval guns used on many British warships and that it was supposedly recovered from the beach of Dunkirk






if anyone could help I would be super grateful.

[BlackCat1982]

If it was recovered using a metal detector then they have broken the law.