World War II Monopoly with real money

Brian McMahon wrote a remarkable piece for Mental Floss about the British Secret Service's master plan during World War 2 to smuggle escape gear to captured Allied soldiers inside Germany using the popular boardgame Monopoly:

In 1941, the British Secret Service approached Waddington with its master plan, and before long, production of a “special edition” Monopoly set was underway. For the top-secret mission, the factory set aside a small, secure room—unknown to the rest of its employees—where skilled craftsmen sat and painstakingly carved small niches and openings into the games’ cardboard boxes. Along with the standard thimble, car, and Scotty dog, the POW version included additional “playing” pieces, such as a metal file, a magnetic compass, and of course, a regional silk escape map, complete with marked safe-houses along the way—all neatly concealed in the game’s box. Even better, some of the Monopoly money was real. Actual German, Italian, and French currency was placed underneath the play money for escapees to use for bribes. Also, because of its collaboration with the International Red Cross, Waddington could track which sets would be delivered to which camps, meaning escape maps specific to the area could be hidden in each game set. Allied soldiers and pilots headed to the front lines were told to look for the special edition game if they were captured. The identifying mark to check for? A red dot in the corner of the Free Parking space.

You can also read a PDF of Brian's story from his website.