Hi, Belgian fineness mark used 1942-1990. A835 in oval frame-shape for Argent, the French word for silver, fineness minimum 835/000. The maker' s or responsibility mark within a barrel frame-shape, introduced 1942 to date. I am afraid I can not identify the maker's mark for after 1942. You can probably find this maker's mark in the book written by; Dievoet, Walter van:
Algemeen repertorium van de edelsmeden en van de merken van edelsmeedwerk in België. Vol. III: 1942-1997. / Repertoire general des orfevres et des marques d'orfevrie en Belgique.