If the metal on this rib is straight and not concave, I would think it would be a type of re-enforcing rib. Again I don't know much about other manufacturers, but L.C. Smith called it just what I stated. This type was on the early L.C.'s and later it was a curved heavier duty piece of metal that was soldered and the curve was near the loop. It was found on Trap grade shotguns and Trap option shotguns and on some Longrange guns.
Here is an example on a Trap Grade that has an extra set of barrels and an extra for-end stamped 2
This is the early style (pre-1902 gun shown) re-enforcing rib or re-enforced loop.
