NEW YORK, NY.- Sara Rivers Cofield was on her usual search for interesting period clothing about a decade ago when she noticed what appeared to be a “textbook” silk bustle dress from the 1800s at an antique mall in Maine.

The bronze-colored dress was in good condition, with a draped skirt, puffy bustle, and metal buttons that appeared to depict a Shakespearean motif. Rivers Cofield, an archaeologist, bought it for $100. Little did she know that the garment also contained a mystery: a secret pocket with a cryptic note.

Part of the message, written on two, scrunched-up translucent sheets of paper, read: “Bismark Omit leafage buck bank / Paul Ramify loamy event false new event.”

Rivers Cofield was baffled. Was it a writing exercise? A list? A code? “What the…?,” she wrote on her blog in 2014. “I’m putting it up here in case there’s some decoding prodigy out there looking for a project.”

Wayne Chan, a data analyst at the University of Manitoba, finally cracked the case. The note, he wrote in a recent study, contained codes used to telegraph condensed weather observations for stations in the United States and Canada in 1888. Each message started with a station location, followed by code words for temperature and pressure, dew point, precipitation and wind direction, cloud observations, wind velocity and sunset observations, Chan wrote.

“For the first time in history, observations from distant locations could be rapidly disseminated, collated, and analyzed to provide a synopsis of the state of weather across an entire nation,” he added. Those observations, however, needed to be condensed — just like other telegrams — into codes.

Chan’s findings brought resolve to a community of online sleuths who for years had speculated about whether the owner of the dress was a spy, a romantic sending coded love notes or a risk-taker engaged in illegal gambling. One cryptologist declared it among the “top 50 unsolved encrypted messages”; another wrote that even the most “voracious code-breaking teeth” had been unable to decipher the messages, which came to be known as the “Silk Dress cryptogram.”

Chan said in an interview that he first worked on the code in the summer of 2018, but gave up after a few months without getting anywhere. At the end of 2022, he revisited it, poring over some 170 telegraphic code books in an attempt to find the answer, to no avail. Another book, with a section detailing signals used by the U.S. Army Signal Corps, seemed to contain examples similar to the note found in the dress. After further research, he was finally able to decode it.

And, lo and behold, it was a weather report.

“When I first thought I cracked it, I did feel really excited,” Chan said, noting that it took a while to build enough evidence to confirm his theory was correct. “It is probably one of the most complex telegraphic codes that I’ve ever seen,” he said.

For example, “Bismark Omit leafage buck bank,” indicated the reading was taken at Bismarck station, in the Dakota Territory. “Omit” was for an air temperature of 56 degrees and pressure of 0.08 inches of mercury, though the National Oceanic and Atmospheric Administration has said the true reading could have been higher. “Leafage” for a dew point of 32 degrees, observed at 10 p.m. “Buck,” clear weather, with no precipitation and a northerly wind. “Bank,” a wind velocity of 12 mph, and a clear sunset.

Old maps helped Chan figure out the exact date of the observations: May 27, 1888.

Some mysteries surrounding the dress, however, remain — including who owned it, and why she would have had weather codes stuffed in a secret pocket.

“It’s tantalizing,” said Rivers Cofield, who found the dress, noting that a name, “Bennet,” was written on a paper tag stitched into the garment.

“Presumably, whoever did that is the last person who owned the dress, and presumably, the last person who owned the dress,” she added, “put the code in the pocket.”

This article originally appeared in The New York Times.