Old fancy shotguns often came in sets, usually two, but sometimes more. A lot of people, myself included, thought this was so you could go hunting with your buddy. No. These are for "double gunning" at driven game shoots. While you are shooting one gun your servant reloads the other one, then you swap. This is faster than reloading yourself. If you were a real badass you might use a set of three identical guns.
https://vault.si.com/vault/1972/05/22/the-game-hog-of-dallowgill