Your rifle has some decent Leman details on it, and is clearly signed on both the lock and barrel, removing any doubt about the maker. The finish is beat up, but original. I think with a little cleaning, and oiling to put color back into the light areas, the stock will look a lot better. It also has good areas of artificial striping left, which seems to be gaining in acceptance or popularity the last few years. Perhaps the patchbox is the biggest issue.
The patchbox finial is not a standard shape for Leman guns, but does have several Leman details. The cavity looks pretty old, but more importantly, the box has a Leman style three segment hinge that's not filed down on the outer ends. It also has Leman's enlarged or domed brass release button in the toe plate. A final Leman detail, altho perhaps minor at best, is that the box's finial screw head is lined up, which Leman did on a number of his rifles.
I think we need to interpret Jim's "several hundred bucks" on the high end with this rifle. I also don't think Jim saw that the gun was a full-stocked rifle, since your pictures of the forestock are taken at a difficult angle to see details, instead of straight over the gun. But the full forestock appears to have ramrod pipes that are relatively evenly spaced, so hopefully little if any of the barrel has been cut off. If it has at least 40 inches of barrel left, it shouldn't hurt value much.
I think, in its current condition, you have a decent $500-plus gun, and with a PROPER surface cleaning and stock oil applied (tung oil works pretty well), the stock will look a lot better and the gun may bring a couple of hundred dollars more. Any cleaning and oiling must be done in a manner that doesn't damage what's left of the original finish and artificial striping. Shelby Gallien