I think a better picture might show that the rifle was broken in half through the lock area.
I'd guess that the original lock and side plate were lost, or beyond use, and at some point someone decided to put the gun back in one piece using this lock and large sideplate to help support the break. A closer look might tell whether the trigger guard and trigger are original, or new replacements. I doubt this work was done by some restorer guy trying to make a buck, but more likely an owner wanting to have the gun back in one piece, so it would be less likely to end up in the trash.
As for the gun, the patchbox finale is very similar to that on my John Parks Sr. rifle.
Also, a last closer look might be to look closely at the wood grain, structure and striping to assure the front part of the gun actually belongs to the back part of the gun.
If it is, and I expect so, a good restoration would certainly improve the look and continued long life of the rifle!
John
