Hello,
I bought this map of the british minefields at an antique shop, IMO its from a book or a newspaper but i could be wrong.
Its very interesting, there is anouther map in the shop along with some maps of the franco prussian war for sale for 5E. I might get them and give one to my aunt for her 50th birthday (she likes war maps).
Hope you enjoy

Map to illustrate the german submarine blockade and the British Minefields as a measure of protectionMap to illustrate the german submarine blockade and the British Minefields as a measure of protectionMap to illustrate the german submarine blockade and the British Minefields as a measure of protection