Sotheby's is having an auction of "Important Judaica" next week. It includes several Hebrew manuscripts. A few items that were sold a few years ago at the Montefiore auction. The earliest extant Yemenite Torah scroll. A Yemenite manuscript of Ketuvim by a member of the Benayah family, who were famed for their scribal skills. A Mahzor Roma (a siddur following the rite of Jews in Rome) that belonged until recently to Prof. Ariel Toaff.
(My thanks to Prof. Jordan Penkower for pointing out an inaccuracy in my description of the Benayah manuscript)