Your weapon is not a flintlock but a percussion cap shotgun rifle made by GG Julcher of Philadelphia PA from c 1840 to the Civil War. It is an unusual weapon as the shotgun lock (Hammer and cap) on the left side is upside down, an extremely clumsy solution as the cap tends to fall off.
Side-by-side shotguns are still manufactured.
Charles Daly's current line of shotguns are manufactured by K.B.I. in Turkey: http://www.charlesdaly.com/faq.asp In the past, Charles Daly has sold shotguns manufactured by Miroku of Japan. But current production shotguns are Turkish.
FN
in the sameplant as berrettas
cresant arms
Meriden Firearms
detriot, mich
Huglu and Remington come to mind
Hunter Arms
Westfield, MA
They were introduced in 1995.