In my searching around, the BSWD markers around Chatham, for instance, all had a broad arrow between W and D.
Coincidentally Fort Halstead, in its modern form, was only mentioned to me on Boxing Day in the context of his friend who works there is very, very tight lipped about what goes on in there
Meanwhile, back at the quiz... Martin's map question led me to set another. This is a rifle range, never shot there myself, but I did have the opportunity in the early 1980s. It was full-bore rifle, .303 or 7.62Nato.