The Riva table: nine cipher letters to Giuseppe Riva, 1721–1727

TASK: take a partial decipherment further: The Riva table: nine cipher letters to Giuseppe Riva, 1721–1727
This page: https://dbourdeau.github.io/cyphersolver/further/riva1722.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/riva1722.html (read it first: how the text was read, the key, the reading)
  Date:       1721–27
  Outcome:    key from adjacent plaintext · partial
  Read now:   85.6% of the deciphered cipher tokens give sense (pieces below may be untouched)
  Files:      https://github.com/dbourdeau/cyphersolver/tree/main/targets/riva1722 (NOTES.md, key, transcription, reading, scripts)

OPEN GAPS (from NOTES.md, "## Remaining gaps")
  1. [open-codes: doable now] Codes: 201 units, 74 different numbers; none is counted read - blocker: open-codes; `holes.md` 2 lists each with the proposed value, if any (only 288 V.S. and 214 Olanda have a gloss of the time)
  2. [illegible: needs a new source] 8 plain/underlined conflicts in the 20 Mar 1726 letter, and the words "n-ma-na-r-la" (21r.L11), "di centena da" (21v.L01), "su fi" (21v.L09) - blocker: illegible; whether a stroke runs under a group is not settled on the 1,400-px images; the full-resolution crops were not re-viewed for this folder
  3. [no-key-material: needs a new source] row 5 of the table: plain 51/52 (ra/ga? re/ge?) against plain 53/54/55 = g (K3); 5_ (chi), 30_ (esser), 50_, 0_, 9_, 9 - blocker: no-key-material; the gloss pairs recorded (`gloss/gloss_pairs.tsv`, 10 pairs) do not decide them; "ingegnarsi", "diligente" and "regenti" need plain 52 = ge
  4. [no-key-material: needs a new source] the K2 rows read off the two glossed letters of 1726 (27 Feb, 6 Mar) - blocker: no-key-material; only 10 gloss pairs and a rough group reading of c. 5r were written down, and the two letters are not transcribed in full, so K2 itself cannot be re-derived from the files (the pair behind 8_ = E, replaced by PER in K3, is not among the ten)
  5. [illegible: needs a new source] Olivazzi 17 Apr 1725: four stretches not read, the right edge of 2v under the facing leaf; 2v is decoded, not read - blocker: illegible
  6. [needs-physical-access: needs a new source] Lindgren 2016 (Il Saggiatore musicale 23/2) not seen - blocker: needs-physical-access; sold by the publisher's platform, needs a library copy; the Modena-side records (Archivio di Stato, cifrari) are the other place a key may survive
  7. [needs-physical-access: needs a new source] Other Riva correspondents: 398 of 535 further records viewed in full, no other letter in this table; 111 recorded as not checked (the folder's figures leave 26 of 535 unaccounted for) - blocker: needs-physical-access; records not reachable from here

ALREADY TRIED (from NOTES.md, "## Escalation")
  [x] siblings: the Estense file for Starhemberg, Selvatico and Olivazzi viewed; the two glossed 1726 letters are the key source; 398 of 535 further Riva records viewed (111 recorded as not checked; 26 unaccounted for), no other letter in this table
  [x] clear-pages: no clear copy of any of the nine letters; the dates written in clear inside the cipher lines of 20 Mar 1726 taken out of the cipher
  [x] known-keys: the 1719 table of `selvatico1719` (its contributor found that it does not read the 1722 letters); K21 of `starhemberg1721` and K3 tried on each other's letters: neither fits
  [x] print: Lindgren and Timms 2003 and Stefani searched in open copies (no cipher); Lindgren 2016 not seen (paywalled), recorded as a gap
  [x] key-rebuild: K2 rebuilt to K3 from context in the 1722 letters (15 rows), 7 unglossed rows dropped; remaining values proposed in `holes.md` 2 and not counted
  [x] retry: every unit not read is listed in `units.tsv` with its reason; the underline conflicts of 20 Mar 1726 left for the full-resolution images (gap 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/riva1722/NOTES.md in full, and the
   key, transcription and reading files it names; lang/README.md (shared language models).
   Work in targets/riva1722/. 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/riva1722/. 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+riva1722&page=riva1722.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.