This is a total guess, but it looks like B?ltom Esar9 (B?ltom Esarus) with the m having a descending curled tail. Maybe an abbreviated name? Like Bart[ol]omé Sarus?
It doesn't look like Voynichese. It doesn't look like 15th-century script either. More like 16th century or early 17th century, although it's really hard to tell.
It's not readable in the current Beinecke scan. It's completely lost in the fold:
It doesn't look like Voynichese. It doesn't look like 15th-century script either. More like 16th century or early 17th century, although it's really hard to tell.
It's not readable in the current Beinecke scan. It's completely lost in the fold: