The Book Switch Theory

[proto57]

 The Marci letter clearly states "Ferdinandi Terty", as in Ferdinand III.

Another fairly minor point, but worth mentioning as it pertains the overall timeline of Marci’s conversation with Raphael is this:
The translation of the letter to English that is provided on Philip Neal’s website is bungled a bit (I’ve expressed doubts about some of those Latin translations before).  The letter says that it was “Ferdinand III”, but also implies that he was at that time King. He became King in, if I remember correctly, 1627. And until -1652. So Marci heard this information from Raphael after 1627 and before 1644 (when Raphael died).

Great catch! That had not occurred to me, and I've never heard this point. It is another great reason to not put these issues to bed, before every last valuable nugget is mined from them.