How Monopoly helped WWII POWs escape

And now for something completely different: Monopoly games that helped American POWs escape German camps:

http://www.eurogamer.net/articles/2014-01-12-inside-monopolys-secret-war-against-the-third-reich

"What he found out along the way is that the tools that most likely would have been used in this set would have been a very small compass, maybe an inch in diameter, and they also would have had files - two different types to get you through fencing material, and probably a folding pair of shears, a very small set of shears that would collapse on a pivot, and then of course a silk escape map that would have been appropriate for whatever camp the delivery was for." Skilled technicians at Waddingtons would have cut precise openings for the tools in the cardboard liner of the game boards, while foreign currency money pads would have been assembled with a few Monopoly bills on top for disguise. Orbanes also says that one of six possible area maps would have been added to each game, and printing marks - a seemingly errant period after a specific location on the board itself that would pass as a production gaff - would have disclosed the kind of map that was inside. A period placed after Mayfair would signal a map of Scandinavia and upper Germany, say, while one after Free Parking referred to Northern France.

What ingenuity that took!