Generally speaking document classification expires after a certain time period unless it gets renewed. for most top secret documents that period is 75 years.

but here's the thing... anything that was sufficiently relevant to national security to renew the lease beyond that period would be so compartmentalized that we wouldn't even know it existed.

i.e. it's something bigger and more concerning than the manhattan project or majestic-12.

so your question is kind of impossible to answer... only the people working with the documents would know about it, and they aren't going to commit a leak in /r/AskHistorians

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