I'm checking BWV 1004 for a project I'm working on. I sometimes see that Anna Magdalena Bach wrote some veeeery strange flats. For example...
Bars 113 and 114 from Chanonne. Bar 113 has on the bass voice: F# G F♮, she writes F# G Fb, then on bars 113-144, highest voice has: D C# | C♮ B♮. She writes D C# | Cb B♮ (which is plain wrong by reading with our current rules).
So I guess that sometimes she means b to "cancel" a previous # and leave it as a ♮? But I find that in some other cases she uses a ♮ to cancel previous #s. Take bar 47: G# A E F G♮ (not that she had to write the ♮, anyway... from what I can gather, JSBach and her wrote all accidentals except on repeated sounds and so if she hadn't written the ♮ that means that she would have wanted a G♮ to play anyway because that's the key signature).
Any general rule that can be applied to figure this out?