A picture can speak a thousand words…including secret messages.

Yesterday we looked at how the Enigma machine is confusingly diagrammed in The Ultimate Spy Book. Today, I want to spotlight a few artifacts that show how images have been used to communicate ulterior meanings.

After chemically stripping the photograph on top, a secret message is revealed. This was used in the 1960s by the East German security service.


The following sketches aren’t merely the casual doodles of a naturalist. They were drawn in 1890 by Robert Baden-Powell (founder of the Boy Scouts) on a clandestine military mission to gather intelligence in the Balkans. The text says, “The veins on the butterfly’s wings contained a plan of the fortifications, while the spots on the veins denoted the size and position of guns. The drawing of the leaf was made to show trench lines.” This is data vis!


These stamps served as clues to help the insider detect trap letters from genuine letters on the French resistance. The detail is a subtle drooping of the bottom eyelid. There’s a joke here that the book doesn’t mention: « Mon œil! » (“My eye!”) is a French expression for disbelief, like “No way!” And pulling down on the bottom eyelid is the gesture to say the same thing.


Microdots are negative photos of text reduced to tiny dots that can then be slipped into the edges of postcards and be read with special microscopes, some small enough to fit in a cigarette. Here’s what a microdot camera and a set of microdots look like, with my average-sized fingertip for scale: