Kennedy: King Gun Sight Co. was one of the top places to get custom sights, action jobs, grips, etc. for handguns (also rifles) into, I believe, the 1950s. Their "Super Target" conversions, as on these two guns, included the vented barrel rib and often a "cockeyed hammer" with a very grippy knurled surface and an offset to the left (for righties) or on the right (for lefties) or on both sides to make single-action cocking faster and surer. I don't remember the details, but I believe there is a complete story about King Gun Sight Co. in the 2004 Shooter's Bible. And yes, Shortcut, the ribs are not removable; and if you did remove one, I imagine it would leave an ugly barrel indeed. These guns are not for the collector looking for factory-original condition.