How did they made these ...in XVI century?

[Claudio HG]

One way to make duplicate parts with matching symmetry is to use filing buttons.

Yes, that is a clever method. Didn't know those, let's say template, were named filing buttons. Thanks, I learned something new.
That seems to be a solution for small parts though, but some parts that you can see in the pictures are quite big. However I just realized that those parts could have been made from casts, and then filed or grinded down to the desired dimension and finishing appearence.

Anyway, I don't know you guys, but I am really fascinated by those old machines and how people did them. I got lost as in a rabbit hole in every museum I visited: London, München, Paris, Milano. The first two are IMHO the absolute best, but they are so large that one would need days to visit them throughly.