This "crowned R" is indeed the Liege, Belgium mark for rifled barrels, canon raye in French, so it was proofed as a black-powder 8 bore elephant rifle. Perhaps it was intnded for use in th the Belgian Congo. The star/S is the personal mark of a proof inspector. The "perron" (from pierre =stone), in fact a pineapple on a pillar, is the age-old symbol of the City of Liege. The ELG in a crowned oval is in use since 1893.
4seventy, b. blindee = jacketed bullet and b.plomb = lead bullet merely denoted the type of bullet a rifle was proofed for, if there was a choice of factory loads in the same case.