Formed by a secret presidential memo in 1952 amid growing Cold War tensions, the fledgling National Security Agency commissioned posters to remind its employees to keep mum about their top-secret work.
Government Attic, a website that requests historical government documents under the Freedom of Information Act and then shares them online, first made the request for the vintage posters in 2016.
Two years on, the US government has released more than 100 security flyers produced between the 1950s and the 1970s.
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The images paint a world of Cold War paranoia, American values under threat and ill-judged pop culture parody.
The informational flyers “were created in-house”, NSA spokesperson Chris Augustine told Quartz. Updated versions “are still used at water coolers, cafeterias, restrooms at NSA’s buildings today”.
Here are some of the most imaginative - and bizarre - retro posters from the newly released archive:
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