Featured on PDR in the collection Barnard’s Universal Criminal Cipher Code (1895)

Barnard’s Universal Criminal Cipher Code for Telegraphic Communication between Chiefs of Police, Sheriffs, Marshals and other Peace Officers of the United States and Canada (1895) was a book of codes to help disguise internal police telegrams in what amounted to some kind of 19th-century version of the encrypted email. Despite first appearances the “cipher” of the book has some sense of order in its "self-indexing" system, as the Preface explains: