TL;DR: Purchasing pens made for a different market can mean some changes are needed to make them fit. In the Japanese market, I often find F nibs thinned to EF and tuned to write glass-smoothly. But, sometimes, I find nibs further turned downward, closer to the Sailor Concord specialty nibs than to the narrow down-turn of the Pilot Falcon or Posting nibs. This rare example of a Montblanc 121 Burgundy with 18k nib, ground from F to EF, turned into a Concord shape, has had artisanal work in these two directions.