Octagonal 4 J
This pen is from the personal collection of Ariel Zuñiga - a generous contributor on FPN, seminal Montblanc collector’s books, and now this website. Watch out for a series of reviews of truly rare pens thanks to AZ’s generosity!
1932 pricelist: J nibs in sizes 2 to 6
Photo credit: Christof C.M.Z. on flickr (link)
For bibliography, see Resources page -->link