I am not convinced by the provenance history of the VMS

[proto57]

Also, Kepler was in the Court of Rudolf, and in his 611 "Dioptrice" actually illustrated the function of a two lens microscope!:

I stand corrected; according to Wikipedia, two-lens microscopes were developed only a couple or decades after the invention of the two-lens telescope, in ~1608.  So it is theoretically possible that a forger in the mid-1600s created a manuscript that pretended to be the work of some forgotten genius who invented the instrument in the 1400s.

We are actually much closer than I thought, if believe this theoretically possible... it is exactly the basis for my theory, if you only substitute "mid-1600s" with "early 1900s". I mean, I didn't realize you were open to a post-1420 origin by hundreds of years, and to a possibility of forgery of optical devices.

(But in that 1611(?) Kepler book, is he describing a microscope, or a telescope?  Unfortunately I cannot read Latin.  From the date I would guess that it was still a telescope...)

Yes, it is a 1611 book (addressing your question mark), and he describes the optical principles of both microscopes and telescopes. He did not name them that, they had other names in his time, and before. But the principles and diagrams of the optical paths and effects are in this book, and were the basis for creating both microscopes and telescopes. And of course, both existed in various forms even before 1611, but not by much. And, again, Kepler was in Rudolf's Court at the time.

Eustice Divini actually based HIS microscope on Proposition 37 of Dioptrice, "Proposition 37: Kepler describes how a single lens or a specific doublet lens configuration can magnify near objects. In 1648, the prominent optical artisan Eustachio Divini built one of the earliest high-power compound microscopes explicitly citing Proposition 37 as his blueprint."

"Propositions 86 and 89: Kepler outlines how combinations of convex lenses can be arranged to show close-up things distinctly, upright, and significantly enlarged."- "You are not allowed to view links. Register or Login to view."

Anyone interested in an English translation of the entire Dioptrice, this one is excellent... and recent. Previously... the past couple of decades!... I had relied on partial translations, and even had often transcribed the Latin for portions, then used Google Translate. Wish I had this, back then!:

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Kepler is mentioned in "Follies..." 21 times, and Dioptrice once. Page 86, "While in the service of Rudolf, Kepler wrote some of his most valuable works; in the treatise on "Optrics and Dioptrics" (1604) [sic] he explained the physics of the eye and the action of lenses...".

we have common ground. On the probable fake nature of the "signature", along with the culprit who put it there. ... So to the "signature", I'll add a possibly supporting, although entirely speculative concept, involving the situation with the "chemical treatment", and the faint nature of the signature to begin with: ...

As a "trailer" for my promised post on that topic:  What made me switch from "just possible" to "highly likely" was a comparison of that signature with that on the "#4" book.  On one hand, the two are just too similar in overall shape, layout, style, etc.  On the other hand, the letters on the VMS are more crooked and uneven, as one would expect in a signature forged by an amateur. 

So here is what I now think happened.  Wilfrid's problem was that there was nothing in the VMS that indicated that it was Baresch's book, much less that it was the "Bacon Original" that Rudolf had allegedly bought for the 600 pazuzas.  No library stamp, no marginal note, no catalog entry.  And no explanation for how a Bacon Original could (1) have got from England to Prague and (2) passed from the Royal library to a nobody like Baresch.  

For (1), he found a barely plausible solution in John Dee, a known Bacon collector who had visited the Emperor in Prague at what looked like to be about the right time. (However Dee returned to England in 1589, which is 10 years before Rudolf's big book purchase identified by Rene, which is probably what Raphael had heard of.)  

For (2), he presumably canvassed the members of Rudolf's court looking for someone who could have taken the book out and whose signature he could forge.  My theory is that he picked Sinapius, because of his role in the Court, and/or because he managed to get what he thought was the doctor's signature from the #4 book that was easily available from the Czech National Library.  He then copied that "signature", changing only the number to #19, as he extrapolated from the likely dates.

But since then we obtained two other books with Jacobus's name on the front page -- from the Strahov library (which would have been much harder to get to).  And one more from the library at Charles University.  And the problem is that the two Strahov "signatures" are in a different hand and language, and none of the first three matches Jacobus's actual legal signature, which is on the fourth one.  And the numbers in those "signatures" are between 4 and 19.

So maybe Wilfrid, after forging the signature, saw copies of some of the other three, and realized that he had copied the wrong signature, with a number that would be hard to explain.  Or maybe he realized that his amateurish forgery would be easily spotted by any handwriting expert, even in 1920.  So he erased the signature, with the excuse of trying to enhance it.  He left only enough of a trace to be barely legible -- but not enough for forensic analysis.

I left all the above intact, and I agree with your reasoning wholeheartedly... we again only disagree on some important details, such the nature of the work which Voynich applied this false signature, and his specific motives: You, on some genuine work he found, to tie it to Horčický and the Court, me, on his forged work, to tie it to Horčický and the Court. I also believe his motivation for choosing Horčický was different than yours, in that I think he was picked because of his role in the Court as described in "Follies...". But we are close on that, too, I think.

Much of your above reasoning is original, but also partially based on the findings of Anton, and you and others, in the excellent discussion on this Ninja thread, started by Anton, and titled "Horčický's books": You are not allowed to view links. Register or Login to view.

I think it would be very hard for anyone to argue that the "signature" is real, as in "by" Horčický, after reading through that thread, and what you wrote above. But if one thinks about it, many who hold that the 1420 Genuine European Cipher Herbal paradigm is the correct one, are nonetheless open to all these: That it is a forgery from some time; that some of the jars may be optical; that some of the content may be microscopic; that the "signature" may be fake, from some time; that it probably has nothing to do with Bacon; that Voynich clearly knew it was not by Bacon; that it may not be the work described and seen by Baresch/Kinner/Marci/Kircher (that the "given" provenance is flawed and/or nonexistent; that it may have been inked hundreds of years past the C14 dating... and more, but the previous is just in this one thread alone.

All the best, Rich