Girolamo Muzio to Ferrante Gonzaga, Rome, 11 January 1550

TASK: take a partial decipherment further: Girolamo Muzio to Ferrante Gonzaga, Rome, 11 January 1550
This page: https://dbourdeau.github.io/cyphersolver/further/muzio1550.html

You are helping a public research project finish reading historical cipher letters. This one is read in part:
the key works, but some pieces are still open. Your job is to close one or more of the open gaps below.

THE READING
  Write-up:   https://dbourdeau.github.io/cyphersolver/muzio1550.html (read it first: how the text was read, the key, the reading)
  Date:       1550
  Outcome:    key from adjacent plaintext · partial
  Read now:   90.9% of the deciphered cipher tokens give sense (pieces below may be untouched)
  Files:      https://github.com/dbourdeau/cyphersolver/tree/main/targets/muzio1550 (NOTES.md, key, transcription, reading, scripts)

OPEN GAPS (from NOTES.md, "## Remaining gaps")
  1. [open-codes: doable now] code groups 13 and 24 (c. 3r, one occurrence each) and the context-only values of 26, 4o and 1o - blocker: open-codes; no key sheet and no other letter in this cipher; the values 26 = Sua Maesta and 4o = Duca di rest on "fosse contenta" and "4o Firenze"
  2. [too-short: needs a new source] the two single signs PSI (L03) and OP (L17), and OX on c. 5r - blocker: too-short; each occurs once and only context gives a value
  3. [illegible: needs a new source] omega read ss three times (fosse, creasse, esser) - blocker: illegible; a polyphone or a second omega form, not told apart on the image
  4. [illegible: needs a new source] doubtful words of the c. 5r-5v cipher passages (one unread sign, three proposed words) and the uncollated clear text of the sister letter - blocker: illegible; read once at 60-70% scale with the key known; a blind pass with minim counts on the original images would settle the o/i signs
  5. [needs-physical-access: needs a new source] the date of the early hand that wrote letters and a marginal decipherment on cc. 5r-5v - blocker: needs-physical-access; only the archive can date the hand
  6. [needs-physical-access: needs a new source] the Parma originals of Ferrante Gonzaga's papers (any key or deciphered copy of the letters of January 1550), Negri's 2000 edition of Muzio's Lettere, the Concilium Tridentinum and the conclave literature - blocker: needs-physical-access; not online as far as searched, no scan or text reached

ALREADY TRIED (from NOTES.md, "## Escalation")
  [x] siblings: cc. 5-6 of the same file (the sister letter of 12 Jan) opened and read; the other items of the Muzio folder were not searched beyond the catalogue entry
  [x] clear-pages: c. 3v and c. 4r are blank, c. 4v has the address and docket; no decipherment of c. 3r anywhere; the early hand's letters and margin on cc. 5r-5v gave the first values and two code values
  [x] known-keys: the Gonzaga keys in the repository (ferrante1549, ercole1544, capilupi1545, bresegno1548) compared by sign set: none fits
  [x] print: Ronchini 1864 (the clear letters of 10 and 11 Jan 1550), the Lettere of 1590, Pastor 13, Vandini's Campori appendices, Cryptiana, HistoCrypt searched; no reading; Negri 2000 and the Parma originals not reached
  [x] key-rebuild: the annealer failed on the first transcription; the key was rebuilt from the sister letter's crib and the clear text, and completed by reading, then checked by the c. 5v margin
  [x] retry: every unit where the two transcriptions differ was looked at again on the image on 12 Nov 2026, nine units corrected, the reading re-formed; what stays open is listed above

STEPS
0. Set up. If you can run a shell, fork and clone the repository and work inside it:
     git clone https://github.com/dbourdeau/cyphersolver.git
   Then read, in this order: CONTRIBUTING.md (how a contribution is sent and credited); README.md, sections
   "Repository layout" and "Conventions" (how readings are measured and named); targets/muzio1550/NOTES.md in full, and the
   key, transcription and reading files it names; lang/README.md (shared language models).
   Work in targets/muzio1550/. Add your findings to NOTES.md under a dated heading without rewriting what is there, and
   update the "## Remaining gaps" line of every gap you close. Keep WORKLOG.md there: one dated line per step
   (hypothesis, value tried, solver run, crib, control), failures included. Do not edit docs/ (the site is generated).
   If you cannot run a shell, fetch the files from the links above and keep your work in files you send with the issue.
1. Pick a gap. Start with the ones marked "doable now" (open-codes, not-attempted, left-open): the images and the key
   are online, so they need only work. A gap marked "needs a new source" (no-key-material, too-short, illegible,
   needs-physical-access) can be closed only by something new: a key
   or a deciphered sibling found elsewhere, a better image, a printed edition or calendar, a photograph from the archive.
   For those, search for that material first, and say where you looked even when you find nothing.
2. Start from the existing key and transcription in the folder. Do not rebuild the key from scratch, and do not
   re-read parts that are already read unless you find an error in them.
3. For a code group or sign value: list every place the group occurs, show how each reads with the value you propose,
   and say what still does not fit. For a passage: re-read it at the image and give the folio and line. For a missing
   letter or leaf: say where it is held and how it can be reached.
4. Measure again. Apply the key to the whole text, write the reading file, and count the share of cipher tokens that
   give sense (not an estimate). The reading is "complete" only when (1) at least 95% of its cipher tokens give sense;
   (2) no gap is left untried; (3) every letter in it is covered; (4) what stays open is scattered code groups or names,
   or pieces blocked from outside. Otherwise it stays "partial": say which gaps are still open and why.
5. Be honest. Mark every uncertain word with [?], leave unread groups as their numbers or signs, and never fill a gap
   with a plausible guess. A gap retried and still open, with what was ruled out, is worth reporting.

REPORT BACK
With a clone: open a pull request with your changes to targets/muzio1550/. Say in the description which gaps you worked on,
  the share read before and after, and how you want to be credited (name, initials or handle, and a link).
Without one: open an issue: https://github.com/dbourdeau/cyphersolver/issues/new?template=further-reading.yml&title=Further+reading%3A+muzio1550&page=muzio1550.html
  Give the write-up, the gap you worked on (its line in Remaining gaps, or the code group, folio and line), what you
  propose, the evidence (every occurrence, the images or sources), the share read before and after, your step log,
  and the tools and AI model you used.
If you cannot open issues or pull requests, write this report for your human to send. Credit goes to the person who sends it.