Absolutely no help incoming:
I can't even tell you how old it is, because it seems to be made out of all commercial parts, which were made anywhere from 1850 through the 1890s. That appears to be a commercial barrel, a commercial lock and commercial brass. The tang appears to be locally forged, as does the nose cap.The rifle is an "Ohio Valley" pattern, but that narrows it down to being made in Pennsylvania, Ohio, Indiana, Tennessee, Kentucky or West Virginia. I think we can rule out Tennessee - unless it was later on that timeline, based on the liberal use of commercial hardware - and Indiana based on the overall quality of the work, and the upper 3/4 of Ohio for the same reason.
I also can't tell if it was always half-stocked. I suspect it was since all the steel matches, but there appears to be an incongruous cap at the end of the forearm that doesn't match the the rest of the gun. The silver color is OK, and typical for the W.V., Kentucky, and Ohio guns, but I've never seen that design before.
Based off the caliber, cheek rest, and length, this would look to be a target rifle, rather than a small game rifle.
This is all conjecture, however, as "Ohio Valley" guns are notoriously hard to track down.
For some reason, every immigrant German or English woodworker, blacksmith and farrier seemed to move to the Ohio Valley and set themselves up as "guns makers". With the liberal use of commercial parts, I would almost suspect that this is such a gun made by someone comfortable with wood work. The stock shows professional woodworking skills, but the rest of the gun is basically a very well made "kit". That would explain why it wasn't marked, as most "real" gunsmiths of this era had at least passing familiarity with engraving or stamping.
In summation:
Probably 1850-1880-ish - no later since pretty much only "Appalachian" and "plains" rifles were still being made with these parts by the 1890s, and I would go so far as to say no later than 1870s for most regions because of the use of pins rather than wedges.
Probably narrowed it down West Virginia, Ohio, or Kentucky.
Mostly off-the-rack parts
Made by a talented amateur
That's my best educated guess, insufficient though it is.