I recently purchased a new Montblanc 11738 fountain pen without a box or any papers. As far as I know and it looks, it is a 144SP sterling silver. What do you think about this pen? Although it's not a piston filler and being a little small in size, it seems to fit well in my hand when posted. I also can't see any differences from a 145 classic other than lacking threads on the barrel. Any info and comments deeply appreciated