Letterlocking in action: A video demonstrating how people in the 16th century built tamper-proof security into their correspondence. Queen Elizabeth I of England, poet and preacher John Donne, Italian businessman Tomaso di Livrieri, and many others used this letter folding and sealing format to protect their private communications.
Letterlocking: Lucy May Schofield’s “Pis'ma-treigol'niki = Letters of triangles,” England (2013)
Letterlocking: Mary Queen of Scots last letter, England (1587)
Letterlocking: Intelligencer Simeon Fox’s Dagger-Trap Letter sent from Venice (1601)
People Protected Messages With Letterlocking

9 Nov 2018. Article by Abigail Cain. Atlas Obscura. https://www.atlasobscura.com/articles/what-did-people-do-before-envelopes-letterlocking

Featured this week in The New York Times: How MIT Libraries’ Jana Dambrogio studies the secret art of letterlocking.
More on letterlocking research at MIT.
Photos: L. Barry Hetherington (Dambrogio); Jana Dambrogio, Collection of H.S.H. Prince Nicolo and HSH Princess Rita Boncompagni Ludovisi, Rome (detail); MIT Libraries (batch of letters)
My Dear this Heart which you behold… A Puzzle
My Dear this Heart which you behold… A Puzzle

After reading about Jana Dambrogio, the Thomas F. Peterson conservator at M.I.T. Libraries, who is analyzing how letter writers have sealed their letters until they reached the intended recipients, I was reminded of a valentine in the Graphic Arts collection. http://www.nytimes.com/2015/09/18/arts/design/a-trove-of-letterlocking-or-vintage-strategies-to-deter-snoops.html Dambrogio has a great…
Marshals’ Returns of Enemy Aliens and Prisoners of War
Q: What made the hole in the middle of this U.S. Marshal’s letter from 1812? A: The damage occurred when the addressee opened the letter which had been sealed closed with a bright red wafer.
This document demonstrates historic letterlocking. Letterlocking refers to a piece of paper written on, folded and sealed shut to create its own envelope.
Many early letters in the National Archives holdings are examples of historic letterlocking, especially letters from heads of state. The photos show a letter listing enemy aliens who reported to the US Marshals’ is from the War of 1812, RG 59 Marshals’ Returns of Enemy Aliens and Prisoners of War, compiled 1812 - 1815.
The series from Record Group 59 contains the returns of U.S. Marshals’ listing enemy aliens who had reported to them. The lists usually show the name, age, and occupation of each alien; the length and places of residence in the United States; the names of members of his family; and the date of his application of naturalization. Included are some receipts from the British consul in Boston for prisoners turned over to him, some lists of prisoners of war delivered to marshals from U.S. ships, and a printed copy of “The Case of Alien Enemies,” 1813.”

Featured this week in The New York Times: How MIT Libraries’ Jana Dambrogio studies the secret art of letterlocking.
More on letterlocking research at MIT.
Photos: L. Barry Hetherington (Dambrogio); Jana Dambrogio, Collection of H.S.H. Prince Nicolo and HSH Princess Rita Boncompagni Ludovisi, Rome (detail); MIT Libraries (batch of letters)
