I have a Manufrance Ideal and I don't recall it having a sling. Mine pulls out of a slot in the base of the stock and attaches to a nicely fashioned hook affair on the upper portion of the barrels. As mentioned, when disengaged it retracts into the stock very neatly. The rib is much like the normal Darne(sunken) but more subdued. I will send you pictures if you want me to email or text them?
Carl