At one time there were around a thousand, maybe more, 'Ateliers' - workshops - in Liége, the gun-making capital of Belgium and still the home of Fabrique Nationale [FN] and a few other high-grade gun makers.
The chances of finding out much more about your fin-de-siécle [19thC] SxS are passing rare. I'll do a bit of digging for you in my old Sears, Roebuck catalogues, but you won't get rich if you are minded to selling it - they cost, originally, anything from around $5 way up to as much as $10.
The ELG over crown dates it after 1854, and the 18,2 is the bore in mm - 12g, as you note. Any chance of all the markings you've missed, and horizontally, please, to save me trying to angle my monitor?
To give you some idea of the prolific output of Belgian gunmakers, the
Banc d’Epreuves de Liege proved 233,526 double barrel smoothbore guns in 1889, the majority for export. In 1899 alone, the U.S. firms of Hartley & Graham and Simmons Hardware bought 90,000 shotguns, rifles, and handguns from Liege gunmakers. Most of the Belgian guns imported before WWI were not of high quality when new, and
NO vintage shotgun should be fired, with any load, until examined by a double gun specialist smith.
Belgian makers
http://www.littlegun.be/arme%20belge/a% ... s%20gb.htm
Maker’s marks
http://www.picturetrail.com/sfx/album/view/18490292
Belgian Trade names
http://damascus-barrels.com/Belgian_Trade_Marks.html
Proof Marks -
Poincons Officiels du Banc D'Epreuves de Liege
http://www.picturetrail.com/sfx/album/view/17575181
Final proof is the crowned
ELG mark.
The
Perron (tower) indicates provisional blackpowder proof even on guns later voluntary proved with smokeless powder; which are marked with a
Lion over PV. If there is no Lion over PV, the gun was NOT proved for smokeless powder.
The usual c. 1900 Belgian 12 gauge bore would be 18.4 mm = .724"
Conversion table - 1 millimeter = 0.0393700787 inches
http://www.convertunits.com/from/mm/to/inches
Date of Manufacture
NON POUR BALLE - choked unrifled bores used
1878 - 1897
1898 - 1910 – Bore in mm (22 cm from breech) and muzzle (choke constriction) appear next to each other after ‘choke’
1910 – 1924 – Bore in mm is over muzzle dimension