Cracking the Code of Letterlocking A tale of Black Chambers and lost correspondence

[DGUtley]

Cracking the Code of Letterlocking - A tale of Black Chambers, lost correspondence, and high technology.


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If you sent a letter in 17th-century Europe, there was a good chance it would pass through one of the continent’s so-called “Black Chambers”—secret rooms attached to post offices and staffed by intelligence units, where mail was opened, copied, resealed, and sent on its way, with the writer and recipient none the wiser. Nadine Akkerman, a senior lecturer at Leiden University, is an expert in 16th- and 17th-century espionage. But during her research into the Black Chambers, she ran across something perplexing—a document by Samuel Morland, a British spymaster, in which he bragged about his talent for opening and resealing letters. “Wait,” she thought to herself. “Can’t we all do that?”


It wasn’t until she met Jana Dambrogio and Daniel Starza Smith—researchers studying letters and document security during this period—that Morland’s braggadocio began to make sense. As it turns out, letters in the 1600s didn’t look exactly like letters today. Mass-produced envelopes weren’t invented until the 1830s, meaning that most 17th-century letter writers folded their correspondence in such a way that it became its own envelope—a process Dambrogio had dubbed “letterlocking.” Letterlocks could be simple, just a series of quick folds without any sort of adhesive. But they could also be incredibly complex, even booby-trapped to reveal evidence of tampering.

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The locking mechanism on DB-1976 was used beginning in the 1500s.
Virtual unfolding showed that it was a low-security locking technique.


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A 17th-century trunk of letters bequeathed to the Dutch postal museum
in The Hague contains an extraordinary archive of 2,600 “locked” letters sent from all over Europe.


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https://www.atlasobscura.com/article...tual-unfolding