You have a nice looking rifle with typical inlay work from the Jamestown school in North Carolina. I agree with Dick's comments on not cleaning, or polishing, anything on the rifle. The Jamestown inlays were usually German silver, which oxidizes to more of a yellowish color, not the blue-black of sterling or coin silver often used in other areas. I can see some color differentiation on the various inlays on your rifle, particularly on the two lozenges on either side of the wrist. While it might be tempting to "even up" the color, if those are replacement inlays they may never match the others closely.
Usually the rear sight sits about over the rear ramrod/entry pipe, and when a barrel is shortened at the breech, the rear sight moves farther backwards as the barrel is slid back and re-breeched. The rifle may have lost its maker's signature when the barrel was shortened. Your rear sight sits pretty far back, so it looks like the barrel was shortened significantly at the breech end... but the 40 inches of barrel remaining looks good for a half-stocked rifle. The lock is a standard hardware store percussion lock ca. 1840-ish, so not quite sure of the comment about a "flint plate" being used... always a percussion plate. Overall, the rifle has nice lines, and exhibits clear details of the Jamestown School in its guard, inlay work, and stocking, so a good rifle, and good choice, to start collecting with. Shelby Gallien