It's not really a perk from Montblanc. I ordered it from an AD where I am a super regular there. This AD is the one which partners very well with Montblanc in Singapore. Maybe that's why they managed to secure #100/100 for me 
(Montblanc doesn't know it was me who asked for this number - it's first come first served!)
And of course I had to act fast! 
Before someone else books that number (#1 was already booked by someone else)
Cheers
Robin