This is both interesting and tricky inscription.
First of all, I would say that ch was written some time after yto ail. This follows from its somewhat smaller size and the change of the direction of its baseline. The appearance is as if ch had to be fit into the little space to the right of ail. Now, if the right margin of this folio has ever been trimmed, this Voynichese ch was inserted after the trimming. Which is interesting implication in itself.
If so, then the whole interesting chain of events expands: someone proficient in Voynichese was inserting important (if of no importance, noone would bother to fit the ch in there) additions at the period of time when the MS already began to undergo trimming.
BTW, note the stain in this very region common for f2 and f3
First of all, I would say that ch was written some time after yto ail. This follows from its somewhat smaller size and the change of the direction of its baseline. The appearance is as if ch had to be fit into the little space to the right of ail. Now, if the right margin of this folio has ever been trimmed, this Voynichese ch was inserted after the trimming. Which is interesting implication in itself.
If so, then the whole interesting chain of events expands: someone proficient in Voynichese was inserting important (if of no importance, noone would bother to fit the ch in there) additions at the period of time when the MS already began to undergo trimming.
BTW, note the stain in this very region common for f2 and f3