Pete Mikalajunas' site is inactive, but I saved his list of Belgian marks.
He had 'LF' as Leroy Brothers (Frères as Raimey suggested) but they are not listed on the littlegun site. Possibly the actioners.
If you would post full size close ups of every mark on the barrel flats, just forward of the flats, and action flats we might be able to provide more information.