The 19th century encrypted message slipped into the secret pocket of a dress, deciphered after years of research

Ten years passed between the discovery, in a 19th century dress, of a paper containing a strange code, and its surprising translation. In 2013, Sara Rivers Cofield, an avid archaeologist who collects antique dresses and handbags, purchased a brown crinoline dress from an antique store in Maine. Returning home, she discovers several pieces of paper hidden in a secret pocket, between the seams of the skirt, but she cannot decipher their secret code. Sara Rivers Cofield then posts a publication on her blog. “I'm putting (the message) here in case there's a decoding prodigy looking for a project.” On December 14, 2023, Wayne Chan, a researcher at the University of Manitoba, broke this mysterious code.

A mystery was gradually woven around these pieces of paper. Internet users, fond of these challenges that span time, tried to decode the incomprehensible lines. For example, it read:

Bismark, omit, leafage, buck, bank

Calgary, Cuba, unguard, confute, duck, fagan

Spring, wilderness, lining, one, reading, novice.

This message has long been considered by cryptogram enthusiasts as one of the “50 unsolved cryptic messages,” according to the United States National Oceanic and Atmospheric Administration. Speculation emerged: it could have been love notes, dress measurements and orders, information about illegal gambling or a secret code used during the war. But the strongest theory involved a type of code related to the new communications infrastructure that began crisscrossing the world in the 1800s: the telegraph.

If the telegraph simplified exchanges between trades around the world, messages had to be condensed and abbreviated for economic reasons. Code books were therefore gradually published for different professions. And particularly for weather observers.

Passionate about code cracking, Wayne Chan, researcher at the University of Manitoba (Canada) and amateur investigator, immersed himself in the mysteries of the “silk dress cryptogram”. After a long, fruitless search through more than 170 telegraph code books, he came across a copy of the Telegraphic Tales and Telegraphic History, which contained a section on the weather code used by the U.S. Army Signal Corps. The words used were exactly like those in the message on the dress.

Each line written on the papers actually indicated weather observations at a given location and time, which were telegraphed to a central Signal Service office in Washington, D.C. Bismark, omit, leafage, buck, bank can thus be translated.

BISMARK Station name: Bismarck, Dakota Territory (in present-day North Dakota)OMIT Air temperature: 56 F Barometric pressure: 0.08 in Hg (Note that only the fractional part of the pressure value was telegraphed , unless the station was west of the 97th meridian or the pressure was less than 29.4 in Hg or greater than 30.38 in Hg). In this case the actual value was 30.08 in Hg.)LEAFAGE Dew point: 32°F Observation time: 10:00 p.m.BUCK Weather condition: Clear Precipitation: None Wind direction: NorthBANK Current speed of the wind: 12 mph Sunset: Clear

The results of Wayne Chan's investigation were published in the journal Cryptologia, and shared by the US National Oceanic and Atmospheric Administration (NOAA) on December 14, 2023. However, some questions remain. Who was this woman? Sara Rivers Cofield notes that the dress is more akin to "casual dress" of the era, which she says indicates that it could have been worn to work. Wayne Chan also found that a number of women worked as clerks in the Army Signal Service offices in Washington, D.C., in the 1880s. Why did she hide these slips of paper in a secret pocket of her dress ? On this side, researchers struggle to find an explanation. The “silk dress” continues to give aficionados of historical mysteries a hard time.