The secret maps used in World War II
bbc.com
bbc.com
They have a 1940s weekend in September where there are a lot of exhibitors and period equipment & 'actors'. There was also a battle demonstration on the fields. It appears to be on 15th and 16th of September this year but doesn't seem to be well publicised at the moment
It's a National Trust property and has a few rooms dedicated to this role, very little was know until recently. It was also Disraeli’s home and has quite a lot of exhibits relating to that era too.
https://www.military-history.org/articles/your-mh-secrets-of...
https://www.nationaltrust.org.uk/hughenden/features/hughende...
There is an image of a map, along with other pictures here https://castlesandcoffeehouses.com/2016/02/13/hughenden-mano...
Granted my grandfather was stationed in London, so maybe the maps of England and other friendly territory were more zoomed in since any citizens you might meet were friendlies.
A great gift as you can centre it on your friend’s house
Maybe I'm not understanding something, but how do you make sure you get shot down in that particular few dozen square kilometers to make the map useful?