In response to a reproduction request that I made for an enciphered letter to the Milan State Archives I also asked candidly and directly about the Voynich. I have received this response->
"The State Archives of Milan preserve a considerable amount of documentation potentially contemporary with the Voynich manuscript. However, these are not mostly codes, but documents (papers and parchments), which
appear to have exclusively content-related affinities with the manuscript you are interested in (e.g.
Sforza scat. 1569 is a collection of materials on astrological topics).
The director
Professor Annalisa Rossi"
Has any Voynich researcher visited the Milan State Archives ever? It is my impression that the Milan Archives have been much slower in digitising its content than some other archives.(As seems to be a common problem with Italian archive.)