A private email from Morocco made me aware of a letter partly in cipher to Cardinal Mathieu Schiner from one of his emissaries. Although it is not known whether Schiner used the same or similar cipher with Rome, the cipher is similar to later Vatican ciphers in being written as a stream of figures without break. This is the earliest specimen of such figure ciphers known to me.
See "An Early Vatican Cipher (1520)" for details.
