I would agree with
@hanshi . He knows stuff!
I think of a "poor boy" as a real minimalist-type rifle... No butt plate, no nosecap, no inlays, and usually fullstocked. I think what you have there is a nice, plain, Midwestern halfstock, a "squirrel rifle," from the late percussion era. If it were stouter, heavier, and had a larger bore, most people would call it a "plains rifle," although that is a term coined by collectors in the mid-twentieth century. Golcher (or Goulcher) is the name of the lockmaker. Locks like that were sold by thousands in hardware stores, and were routinely used by the gunsmiths of that period. I have no idea about the ".L." mark. So many old, handmade guns have little or nothing to go on with regard to identification of the maker.
If that rifle was recently (within the last 50-75 years or so) restocked, it was very professionally done by someone who not only had the skills, but the knowledge to build a stock of the appropriate style.
It may be worth your while to look through Curtis Johnson's books on the gunmakers of Illinois. I believe this is in two volumes. The books are pretty expensive, but you might borrow them through interlibrary loan. Mr. Johnson is the foremost authority on the muzzleloading rifles of that region.
Rifles of this type are under-appreciated, in my opinion, and under-valued. You still see nice ones up for sale and on auction sites for just a few hundred dollars. Yet, they are historically significant in their own right.
That one looks to be in pretty good shape. It won't hurt it to shoot it if appropriate loads are used, followed by proper cleaning.
Thanks for showing your rifle!
Notchy Bob