I think most, if not all of the lines running northeast to southwest are wood grain, including the top of the F. All of the horizontal lines of the letters are perfectly parallel to the grain. Put another way, if the four vertical lines weren't there, would we notice anything there at all?
Here are a few more shots in the sunlight. Don't think they are much help though. It's tough.
I do know the joy of an unexpected find..in budget! I hope you are able to get the pieces parts you need. And yes, as a librarian..I can tell you reference books for the win!! Very helpful for me when we were clearing out my grandparents home. I knew the depression glass and could correctly price it. Lost some on the pull toys but made it up in the hats we sold..Grands house was in Petoskey..had barn,stable,tack room, basement, first/second floor and attic..holey moley the stuff!!!
I believe I have identified a possible soldier connected to this rifle. The last owner recently died and I have researched his ancestry. He had only two Confederate ancestors, both, oddly enough, with the initials of J. T.
Of the two, one's record in the 2nd NC Infantry shows that in Oct, 1863, his pay was docked for a number of items "unaccounted for." These included his bayonet, cap box and 20 cartridges, but his rifle was not mentioned. In Dec, 1863 he was transferred to a cavalry regiment. This rifle would not be likely used by cavalry.
The other soldier, Jackson Townsend, was in the 51st NC Infantry for the duration of the war. He is my likely candidate.
I know it looks like the last "letter" of the marks could be an H, but there is no name in the ancestry beginning with an H, except one, who was in Denmark.
Of course, it could have come into the family's possession after the war.