In the summer of 1915, a wireless telegraph station in Sayville, Long Island owned by the German company Telefunken was caught sending covert commands to U-Boats patrolling the Atlantic Ocean. The transmission device was recovered, but it still isn't clear what it is or how the messages were sent. The mystery box is in the Henry Ford Museum in Detroit, and though they haven't been able to identify the specific properties of the item, it seems like it should be possible based on the specifics of the machine itself.
The details that are available, plus pictures, are all here, and our site (including details about the project) can be found on the project page. We're hoping a specific identification of the object's mechanism can be determined based on the following clues (from the description pages, above): it is a "light-tight wooden box containing a neon yellow, paper tape reel. When the Museum’s conservation department initially opened the box, the paper tape began fading to a near-white pale yellow, leading them to believe that the tape was treated with cyanide. Kristen Gallerneaux, Curator of Communication and IT at the Henry Ford Museum, first thought of the cyanotype process. But her search for evidence of cyanotype paper-tape devices in radio and wireless history came up with nothing."
Does anyone know of other analogous processes used historicaly similar to the setup described? Are there precedents in the history of covert communications in WWI for non-cyanotype communications methods that might apply to this object?