British Codebreakers' Keys of French Ciphers during the War of American Revolution

Back in 2015, I reported use of four codes by the French during the American Revolutionary War in "Code Switching in French Diplomatic Correspondence and Intercepted Letter of Barbé-Marbois (1782)". (By the way, code switching, the theme of the article, was also prescribed during the reign of Louis XIV, as reported by Jörg Ulbert, quoted in "Code Switching in French Diplomatic Correspondence during the Peace Negotiation at Rijswijk (1696-1697)").
To facilitate identifying the four codes, labelled A-D in my article, the letter "E" is assigned the following numbers according to my reconstruction:
Code A: E=94, 395, 709, 865, 1043
Code B: E=302, 461, 590, 871
Code C: E=164
Code D: E=51, 475, 485

I noticed related keys are among the collection in BL, Add MS 32263:
f.220-225 (DECODE* R7681)
f.226-227 (DECODE R7682)
f.228-229 (DECODE R7683)
f.230-231 (DECODE R7684)
f.234-235 (DECODE R7687)
Of these, the "left" key in R7687 matches Code C and the "left" key in R7683 matches Code D. I was hoping the British codebreakers' keys might shed light on the indication system for code switching, but I have not been able to find a clue. (In particular, I thought "867" might be an indicator for Code D, but I find nothing to support it.)

As a starting point for future search, the following describes these items.
R7682, R7683, R7684, and R7687 are the British codebreakers' key worksheets, with printed numbers 1 - 1100. It seems to cover two different codes, one written left to the number and the other written right to the number.

R7682

Endorsed "... Luzerne a Verg[enne]s April 1780 ..."

R7683

The "left" key matches Code D.
Endorsed "De La Luzerne a Montmorin, Nov^r 1780" In a different hand, "Vergennes" is written above the name, and "Luz-ne a Vergennes Dec^re[?] 1783.

R7684

Endorsed "C^te de Rochambeau avec la Chevalier de la Luzerne, July 1781"

R7687

Endorsed "Luzerne et Marbois au Marquis de Castiris 1782"
The left key corresponds to Code C.

R7681

Endorsed "Oct. 1780 Luzerne à Verg[ennes] Philad[elphia]"
This includes many substitution alphabets (but Codes A-D are not among them). The following lists the working title (?) and the "E" section. (It should be noted that sometimes it is not clear which lines belong to the section. In the first place, the same number occurs multiple times, and the meaning of the list is not completely clear.)


"587 la" 272 270 -- 135 187
705 718 -- 24 17

"361 de" 17 634 -- 267 270
817 533 -- 402 250 116 339 -- 616 522
267 87 -- 211 185
"250 l" 361 402 -- 740 135

"607 le" 587 240 -- 305 801
211 185 -- 817 303
"794 de" 961 632 -- 951 449

"816 C" [None. Though "e" is the most frequent letter, it often occurs in syllables and so it is possible that "e" does not occur in a short specimen.]

"1125 de" 28 386 -- 451
"144 Ameriq" 985 401 -- 285 751

"377 B" [None.]

"670 de la" 119_ 767 -- 430 486 342 139 -- 207 49
672 900 -- 588 869

"223" 369_ 1021 -- 290 119_

"342" 143 1070 -- 315 439
903 869 -- 139 670

"103 de" 1 767 -- 516 426
293 591 -- 903 869

"767 gs[?]" 162 1133 -- 802 63
290 119_ -- 670 430
481 1 -- 103 516
799 898 -- 253 369

"297" [None]

"812 des" [None]

*DECODE
Héder, M ; Megyesi, B. The DECODE Database of Historical Ciphers and Keys: Version 2. In: Dahlke, C; Megyesi, B (eds.) Proceedings of the 5th International Conference on Historical Cryptology HistoCrypt 2022. Linkoping, Sweden : LiU E-Press (2022) pp. 111-114. , 4 p. [pdf] Megyesi Beáta, Esslinger Bernhard, Fornés Alicia, Kopal Nils, Láng Benedek, Lasry George, Leeuw Karl de, Pettersson Eva, Wacker Arno, Waldispühl Michelle. Decryption of historical manuscripts: the DECRYPT project. CRYPTOLOGIA 44 : 6 pp. 545-559. , 15 p. (2020) [link] Megyesi, B., Blomqvist, N., and Pettersson, E. (2019) The DECODE Database: Collection of Historical Ciphers and Keys. In Proceedings of the 2nd International Conference on Historical Cryptology. HistoCrypt 2019, June 23-25, 2019, Mons, Belgium. NEALT Proceedings Series 37, Linköping Electronic Press. [pdf]