No. 6 Long Safety
This pen is from the personal collection of Joudenali. Watch out for reviews of truly rare pens from his treasure chest!
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The hard rubber No. 6 long was manufactured in Hamburg from 1924 to 1928, and it measures the same 14 cm capped and 19 cm posted as the No. 4 long. However, the No. 6 nib was larger. Collectible Stars I claims that all these pens that were available in black, were also made in red marbled colour (2x more valuable than black) and even coral red (3x more valuable than black).
The red marbled colour in the No. 6 size is so rare that I haven't been able to find an example in any of the reference books on Montblanc. In fact, Jordi said that he only knows about maybe two more No. 6 long pens in red marbled colour out there.
The turning knob imprint says "6F", which corresponds to the nib size on the pen, which is a beautiful 14k heart-holed nib that is period correct.