The B mark in Belgian proof marks was not supposed to be used to indicate a Belgian Origin. The Liege proof testing range marks should allow to be sure it's a Belgian gun.
If those marks are Belgian marks, each a letter with a crown upon it, they should be the personal marks identifying the official appointed controllers who proof tested the gun.
Are those marks looking likt that one ?
http://mallorquina.pagesperso-orange.fr/source/be12.jpg 
