Rh400, I have no information on JBL Arms, but I do have a reference to a 2008 James Julia (U.S.A.) auction where an AyA two barreled set (c. 1973) marked "JBL Arms Co. Davenport - Iowa." was sold. Could it be the same outfit (perhaps they moved)?
This would indicate that JBL was an importer and reseller. If this is the case then your gun should have proof marks on the frame and barrels near the breech. If you can post a picture of the proof marks, or provide an accurate written description of them then we can determine the country of origin and maybe more info. Knowing which company or at least in which country the gun was made will be more helpful than info on a now defunct importer.
Sharptail