Something similar to f57v.

[DG97EEB]

And f49+f56 are a bifolium, which is nearly but not quite...

There's a great paper available here You are not allowed to view links. Register or Login to view.

It discusses exactly these kinds of diagrams and has a lot of pictures embedded. I've put the most relevant ones on a collage .


Still working through it but might pique some interest (I'd be surprised if every diagram hasn't been looked at individually here previously, but just in case)