Francesco di Giorgio Martini's sketchbook

[Koen G]

I've said it before, there is something profoundly odd about the sketchbooks of all those military engineers. Why is their content so similar or even identical? I feel they all used a similar stack of resources and/or copied from each other. Taccola was known to collect a lot of available older works to draw upon. The question is - did the VM artist use those older sources, or the actual sketchbooks of Taccola and even Martini?
If we accept Francesco di Giorgio Martini as source, this would push the creation date of the VM to the end of the 15th century. Is that plausible? Certainly not impossible, but still odd.

This is driving me insane. Whenever someone posts a new one, I'm sure I've seen it before, while I haven't. Just because they start exactly copying from one another at random intervals.  They're all cooking with the same ingredients. But when they copy, it's such a good copy that you might as well be reading the other guy.