Mary of Guise's Ciphers

I updated "Ciphers during the Reign of Queen Elizabeth I".
V. Nachef, J. Patarin, and A. Dubois-Nayt, "Mary of Guise's Enciphered Letters" reconstructed two ciphers used by Mary of Guise (mother of Mary, Queen of Scots). I found one of them is the same as the one in SP53/23 in the British National Archives.

The Cipher between Marie-Antoinette and Fersen Shared with Marquis of Bouillé

David Chelli found a hitherto undeciphered letter related to the Flight to Varennes and deciphered it. It showed that the cipher between Marie-Antoinette and Axel von Fersen was also used between Fersen and the Marquis of Bouillé. I mentioned this in "Ciphers of Marie-Antoinette and Axel von Fersen".
Moreover, according to Marie-Amélie Brocard's report of this finding, the key word of the cipher was conveyed by indicating a page number of a book agreed in advance, though I could not find its source. I also mentioned this in the above article.

Louis XIV's Undeciphered Letter to his Ambassador in Rome (1690)

Louis XIV's secret instructions to Charles d'Albert d'Ailly, Duke of Chaulnes (Wikipedia), French ambassador in Rome, dated 10 July 1690. The letter is presented on a French website. While I was preparing the relevant updates to
"French Ciphers during the Reign of Louis XIV" and
"Unsolved Historical Ciphers",
discussion started in Klausis Krypto Kolumne, where it should be continued.