Most of the time, he appears to have also misspelled various things in his many plaintext letters, and generally the same things consistently, shared between en

Most of the time, he appears to have also misspelled various things in his many plaintext letters, and generally the same things consistently, shared between encrypted and plaintext writing. They had the opposite effect of hardening the cipher and actually served as perfect "cribs" to aid decryption [1]. There are some occasions where a word is spelled correctly in one place and incorrectly in another, but this isn't necessarily anomalous for people who don't write or read very often or don't have a lot of spelling memorized. In some cases they might even be using some words they've only heard and spoken and never seen before (or only decades prior), and then might see the correct spelling later, or look it up. There's also the possibility he did it consistently because he wanted to mislead police about his knowledge/education/region. Haven't dug into it or anything, but I could definitely see either one being true (genuine mistake vs. subterfuge). [1] https://en.wikipedia.org/wiki/Crib_(cryptanalysis) https://en.wikipedia.org/wiki/Crib_(cryptanalysis)