Here's what remains of the mark
I do not think it is the Birmingham nor London provisional proof mark, and have never seen a "Washington" pattern on an English made gun.
It is probably the tube maker's mark, which was usually filed away from the "rough forged tube" with finishing.
This is Heuse-Riga Fils
This is a spangled JL the significance of which is unknown. Jonlet & Louet were Liege gunmakers. Jean Lahaye-Marbaise was a barrel maker in Fraipont. It doesn't look like the star as the 'points' are inward.
The Banc D'Epreuves de Liege provisional proof mark has been found on some early Lefevers
I am most certainly open to other opinions.
