https://devblogs.microsoft.com/oldnewthing/20220426-00/?p=10...
(spoilers:) during a collab between Microsoft and IBM, Microsoft engineers were frustrated with the coffee at IBM's offices. IBM refused to let them set up their own coffee pot, but IBM was not allowed to look at anything marked "confidential". so they put a cardboard box over the coffee pot and wrote "confidential" on the side.