Fakery?

[Linda]

Would you say that making an unreadable book and selling it with a cipher key was common back then? Tjere is not much sense in writing one book and selling multiple copies of the key. It makes little sense for the owner to transcribe the key and keep it with the book.It seems dicey. 

The VM may be put together like a pocket reference book, but it makes little sense to be one. An encrypted volume means that the key is kept elsewhere and the two need to be brought together, at least once. I would think that once decrypted, the owner would put in readable margin notes. That way, even if the book was taken and the key left at home, there would be something to jog the memory.

The VM does not appear to be refined enough, nor important enough to to be some sort occult work.

Finally, if the manuscript required a key to decypher, can you imagine the when the buyer decodes the text and it disappoints.

I don't think so, and I don't think anyone said that or would say that. Plus you don't need a key if you know how it works already. That is why I think it is a personal (or familial) encoded template. The owner doesn't need to make notes, the owner is likely the encryptor and it was probably meant for their own use. Later finders of it, after all who understood it were gone might have sold it, but I don't think the makers did. There are all sorts of mnemonics, like scorpion tails on plants that probably mean the plant will sting you...to jog the memory. Since the mnemonics were employed by the makers, it would take little to jog their memory, whereas someone else might not even know a mnemonic had been employed at all, which would be the intended result.