A Codebook for Encoding Commerce Info into 13 Figures

I acquired a codebook for encoding sentences for commerce into 13 figures. Such a kind of codebook was common during the age of telegraphy (see "Figure Codes and Code Condensers -- Data Compression Before Computer Age"). For this particular codebook, an example 13-digit figure 011230135435 (excepting the 13th check digit) may consist of:
01 We offer you
123 articles (to be agreed between correspondents)
013 to be shipped in January-February in five cases
54 at 0.63 yen (presumably per some agreed unit)
35 This is the best possible offer we can get for it.

As it turned out, this is the same as an attachment in Chapter XL of 山口造酒・白井健次『英文商業通信寶鑑　附十三数字組立暗号電報』（1922）, noted in an article in Japanese.

Deriving a Fake Message from Ciphertext: 16th-century Venetian Example

Suppose you are arrested by the Russian authorities with a letter in cipher which reads: "Down with Putin". Pressed hard to divulge the plaintext, you confess a fake plaintext: "Long Live Putin."
However absurd it may seem, cryptologically, it is quite easy. All you need is the Vigenere cipher with a meaningless key sequence. The Vigenere cipher amounts to an addition: C (ciphertext) = P (plaintext) + K (key). So, given a ciphertext (C) and whatever plaintext you want to reveal (P), you can find a key K = C - P that supports your fake reading.

Such a scheme, called Falso Scontro, was officially adopted in 1587 by the Venetan Republic, according to Paolo Bonavoglia, "The Enigma of Franceschi's Falso Scontro" (HystoCrypt 2022), Section 6. Bonavoglia's interpretation of how it works (Mode 1) is detailed in Section 8.1. (The base cipher may not be the same as Vigenere, but it is not essential.)
1. Alice and Bob somehow agree on a secret key K.
2. Alice enciphers a plaintext P by C = P + K. She also derives a fake key FK to produce a fake plaintext FP from the same ciphertext C: FK = C - FP.
3. Alice sends C and FK to Bob.
4. If the message arrives safely, Bob can use the pre-arranged secret key K to recover the true plaintext: P = C - K. (If Bob is forced to decipher, he can use FK to produce the fake plaintext FP.)
5. When Bob writes back to Alice, he can use FK as the new secret key, and repeat the steps 2-4. (So, the fake key FK, if safely received, also works as a future key.)

Although this is interesting, it appears to have never been used (Section 10).