I mentioned a recent solution (by Norbert) of Cardinal Richelieu's cipher letter from 1641 in "Unsolved Historical Ciphers". While Richelieu is said to have used the Cardan grille, this is the first specific cipher used in Richelieu's correspondence known to me. Basically, it is a homophonic substitution cipher that has numbers, letters, and other symbols to represent the letters of the alphabet.
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