The proof mark is German commercial proof.

It was the smokeless powder proof for a rifled bbl.
..But the mark was only used up until 1912.
(mid 1893 when manditory proof went into effect until 1912 when the marking was changed)

I don't know that FN/Liege was making a (licensed) Model 98 action in or before 1912. If they were I can't recall any.

My guess would be that a 98 action that recv'd that early of a proof mark was an Oberndorf Mauser mfg.