I'm pretty sure that is Wetzlaub & Jadg,
http://www.gravuren-amthor.de/amthor/fro...ulnd5u670o64ho0 , type engraving with Jadg being the game scene on the sideplates of the A&D boxlock. Being devoid of sling swivels and name and steel type names on the case placard, I would guess it was an export sporting arm and possible for the U.S. of A., but it still has cocking indicators which may not be noticed. If so, there is a pretty good probability that the chambers are 70mm and I would ask for a image of the flats and of the ejector/extractor.
Kind Regards,
Raimey
rse