I beg to differ that it was a conversion from flint to percussion. I don't see any holes on the lockplate that suggests a frizzen spring on it.
It was mentioned that the front of the barrel is secured with a barrel band. This is very unusual for a non-military gun. I'm wondering if that was a repair because the pin or wedges beneath the barrel weren't holding the gun (barrel to stock) together.
How about a full length photo.
Any patchbox or a grease hole on the side. Take a picture of the cheekpiece too. Betcha it's some sort of schimmel/poor boy.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!