Should the "600 ducats" part of the Rudolf story be dismissed for good?

[ReneZ]

After all, would Marci expect an Italian scholar to know the value of an amount 70 years earlier in another country?

This is especially true with respect to the amount of 500 silver Talers, because the Taler was only worth a fraction of its original value by then.

On the second post related to worrying about the value of the item received, perhaps your thought is a modern one, but it appears that Marci countered any such worry in his letter.
He clearly states that he inherited it from someone who is no longer alive (as usual I suppose) and he is giving it to Kircher as a present.
On top of that, Kircher was quite used to receiving gifts to be added to his museum.