So many mistakes in spellings and nomenclature in the book, though. Should we expect that there would be a correct abbreviation of Monsieur when the 1960 book has Mons. Florin and the later book has Mons Florin? Just like Madam butterfly which is spelled both as Madam and Madame in the later book, with several other similar happenings. I think it's still onward through the fog, but I still suspect it was meant to be Monsieur. Even in the wiki there's a Mons Mayne as well, giving suspicion that it could be meant to be Monsieur (as Marie also brought up).