[Luc]

> [...] the maker was almost certainly a transcriber who used it to keep his place on the page and note the column he was writing in when he stopped. The wheel would be moved to the stopping point and the circle turned to the number of the column he had been writing in when he stopped.

It would make a lot more sense that the bookmark was placed in the source book rather than in the copy. I.e. the wheel would be turned to the source column they had been reading from.

[pseudohadamard]

Would that be necessary though? You've already got the perfect bookmark, all you'd need to do is check where in the copy the text stops and continue from there in the source. At most you'd need to bookmark the source page, but in theory not even that.

[Luc]

This style of bookmark is rare so it follows it wasn't _necessary_. But with dense text it might be faster and perhaps less error prone than locating the right place in the text?

Scribe would change the margin size and line spacing, and the parchment would be a different size than the source, so the page breaks would end up in different locations in the text.

[thomascountz]

I imagined the same; and in that case, it wouldn't need to follow that it was transcriber's bookmark.

[klimt01]

The other instrument, a pencil-beam light.