Jim, seems a pity no one has commented on this unusual and interesting item. So despite knowing very little about pistols, I will see if I can get the ball rolling again ...
Presumably Bangor, Maine, USA was named after Bangor in Wales ? To all appearances this odd looking pistol would not be very practical, especially if kept in a holster. A derringer type job (easily concealed), preferably with more than one barrel, or a pepperbox, or an early revolver would be much better. Picture a brawl in a logging camp... some hulking brute coming for you with a pick-axe , you have discharged your single shot and it has either missed or not stopped him ... nasty
Hope some pistols experts can contribute to your post...