Did the Montblanc No. 94 also exist in solid white gold, and what does the unusual hallmark 580 instead of the usual 585 mean?

A white-gold variant of the No. 94 (around 1965) counts as very rare and is not documented in the relevant Montblanc book either. The hallmark 580 instead of 585 is in the jewellery area unusual but occurs on some historical gold alloys. That corresponds to a gold content of about 13.6 carat instead of the usual 14 carat (585). Such pieces count as rarities that even experienced collectors have so far not encountered.