LIST 30 10 Oldest Still-Classified Documents at the National Archives

As of the beginning of 2004, these are the oldest classified documents in possession of the National Archives and Records Administration. If you're wondering how 85-year-old information on naval mines and German invisible ink can still represent such a threat to the republic that it must remain top-secret, you're not alone.

1

memo: Heingelman to Marlenck (October 30, 1917)

2

report: “Detection of Secret Ink” (January 1, 1918)

3

pamphlet on invisible photography and writing, synthetic ink, and other topics (January 1, 1918)

4

“US Naval Mines, Mine Anchor, Mark VI” (January 26, 1918)

5

report: “Secret Inks” (March 16, 1918)

6

“US Naval Mines, Mine Anchor, Mark VI” (May 1, 1918)

7

Ordnance Pamphlet 575: “Enemy Mines” (June 1, 1918)

8 9

report: “German Secret Ink Formula” (June 14, 1918) (one-page and three-page versions)

10

Ordnance Pamphlet 643: “Mine Mark VI and Mods., Description and Operation” (January 1, 1938) images

Thanks to Michael Ravnitzky