Great find! Not a common razor for sure. I remember reading that at the beginning of frameback razors, most believed they were cheap razors. The lack of grinding and basically just putting 2 piece of metal together didnt require the skill of grinding a razor from a blank.
Jacques Lecoultre changed all that, the quality of his razors, and the ease of maintaining the edge, like a full hollow razor without the meat of a wedge, made these razors very popular.