The markings are "reproof" marks, circa 1893-1925: bearing both Birmingham, England (crown/R), and Liege, Belgium (i.e. the Liege mercat cross for the provisional proof, and crown/ELG in oval for the definitive proof). The Merchandise Marks Act of 1887 required all foreign-made guns to be re-proofed before they could be resold domestically or for export. For example, a gun made in Birmingham may be proved in London, and a foreign-made gun may bear the Birmingham or the London Proof Mark, therefore that the proof mark is not an indication of origin, but simply a test made at a certain place.
For although English, Belgian, and German Proof Marks frank guns of English, Belgian, and German manufacture in all three countries, a gun of English manufacture bearing a Belgian or German Proof Mark only is an “unproved” gun, if offered for sale in England as an English gun. Like postal letters, guns must bear the stamp of the country of their origin. -- [The Causes of Decay in a British Industry” (1907) by “Artifex” and “Opifex”]