A quick look in my reference books shows three listings for the name FOX, just plain FOX, a Trade Mark used by the J. Stevens Arms & Tool Company on hammerless doubles made between 1925 and 1935; A.H. FOXGUN COMPANY Philadelphia, PA based gun maker from 1907 to 1929 (bought by Savage Arms Company in 1930) and C. H.Fox, a knock off name used on guns made by the American Gun Company. None of these guns had under levers. I suspect the gun is of European origin, perhaps Belgium made. Look on the bottom of the barrels for proof marks. I suspect you will find Belgium proofs which consist of the letters"ELG" in an oval with a crown on top.