Hi all. As with the shell I posted a few days ago, I was given this lid by a relative who visited the WW1 battlefields many years ago. It has sat in his shed ever since. I decided to clean it up by bathing it in lemon juice and was surprised to see that it appears to be made of copper. As the pics show it has six rivets on top. All my attempts to research this have failed, so can anyone hazard a guess? Unfortunately I don't know where it was found so have no idea as to nationality. Any help would be greatly appreciated.