Not established to Not established, 18th century?

01 The letter

02 The key

37 symbols, 36 letter signs, 1 ligature; 2 unidentified signs The key was recovered from the ciphertext alone.

03 The decipherment

p351

soies sure, que vous aures reusi dans vos entrepresi, enco[r] vous seres heureux, si vous non feres acun mau vaise usage —

Translation. Be assured that you will have succeeded in your undertakings, and that you will be happy if you make no bad use of it.

p351

Ceux, qui auront le bonheur, de décou[v]rir cet secret, seront heureux, etant bon chretien, et suivant ce, qui suit —

Translation. Those fortunate enough to discover this secret will be happy, provided they are good Christians and follow what comes next.

04 Our check

This result is George Lasry’s. This project did not re-solve the cipher: it checked one sample against the Gallica image and recorded what it found.

• Batch A. Image checked: https://gallica.bnf.fr/ark:/12148/btv1b525172213/f393.item
• Folio matches the report: yes; cipher present: yes
• What we checked: p.351 line 1 "C?TD, L T φ ..." -> "Ceux, qui ..." with his key (L=q,T=u,φ=i); recurrent group "P X T Y" = v o u s throughout; consistent with his excerpts "Ceux, qui auront le bonheur ... vous"
• Verdict: confirmed (method key recovered from ciphertext-only, extent partial). The check is a sample, not a re-solution.
• Notes: 93.3% identified (61 ?), so below the complete bar. Alchemical recipe, page ends with a flourish; date "18th century?" unverified.

05 Sources

• George Lasry, with ChatGPT Astra 6 and Anthropic Opus 5.5, BnF cipher research, 10 October 2026 (sent to Daniel Bourdeau on 13 October 2026 for publication here), p. 18; his other items are listed on his contributor card.
• The working folder: targets/fr14765p351/ (his entry as extracted from the report, our spot-check, profile.json).