As long as they were at it, the clever workmen at Waddington's also managed to add:
1. A playing token, containing a small magnetic compass
2. A two-part metal file that could easily be screwed together
3. Useful amounts of genuine high-denomination German, Italian, and French currency, hidden within the piles of Monopoly money!
British and American air crews were advised, before taking off on their first mission, how to identify a 'rigged' Monopoly set -- by means of a tiny red dot, one cleverly rigged to look like an ordinary printing glitch, located in the corner of the Free Parking square.
Of the estimated 35,000 Allied POWS who successfully escaped, an estimated one-third were aided in their flight by the rigged Monopoly sets. Everyone who did so was sworn to secrecy indefinitely, since the British Government might want to use this highly successful ruse in still another, future war.
The story wasn't declassified until 2007, when the surviving craftsmen from Waddington's, as well as the firm itself, were finally honored in a public ceremony.
It's always nice when you can play that 'Get Out of Jail' Free' card!
I realize that many of you are (probably) too young to have any personal connection to WWII (Dec.'41 to Aug.'45), but this is still an interesting bit of history.