I would surmise it may have been made for the India trade - that is, English Officers being stationed in India. The side by side would have been used with shot for fowl as well as with balls for big game - normal stuff. Later on, they'd load only one tube with shot - the other a ball.
The pistol would be for close pretection ( &lovely it is), if needed due to failure of the 'pelter's' load to stop a beast - man or animal. My opinion.