W. & C. Scott was one of the most important gunmakers of the last 200 years. In the their history they came up with many different designs for doubles. One of the quirkiest was the Quintuple Grip system you can see on this shotgun.
This system combined a standard Purdey-bolt with two bolts on the outside of the action and barrels. It was used on a number of guns in the 1880s and makers like Holland & Holland also used it on a few of their hammerguns.
It’s an intersting design, but not very practical. The gun itself is clunky, and I doubt the exteral bolts are an advantage.