This could have been from the Brunswick factory, but I haven't seen a 2-piece Brunswick joint done like this. It came from a source that had Rambows and also a lot of 1942-60 Brunswick Hoppe Pros, apparently brought home from the shop by an employee (my speculation). It arrived in a 1950's Brunswick tube with brief repair instructions (repairs were never done). The problem was a 6" split from the bottom of the butt on both sides that probably resulted from someone removing weight and forcing a dowel in that was too wide.
I added weight, repaired the butt and refinished with French polish:
I added weight, repaired the butt and refinished with French polish: