During WW2 the US Playing Card Company, working with the Office of Strategic Services & MI9 created a deck of cards to aid Allied prisoners of war escape from German POW camps. When the cards were soaked in water, they separated to reveal a portion of a map of Europe. An escapee would need to piece together a whole map from multiple cards. This escape aid helped at least 32 people escape from Colditz Castle & prompted some 316 escape attempts.

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#MI9
#OSS
#Colditz

https://www.spymuseum.org/exhibition-experiences/about-the-collection/collection-highlights/bicycle-r-escape-map-cards/