As they said, it was made on the same general design as the early U. S. Gardner gun from the post-Civil War period, which was later adopted by the Royal Navy. Gardners first had a single barrel, and later dual barrels, as the Bira has. That was one of the most interesting items I have seen on Pawn Stars. If Rick really and truly got the Bira for $20K, it's a real bargain. I wouldn't have hesitated to pay the original asking price of $30K. Or the whole transaction could have been staged.
The most interesting feature of the Bira Gun was the flat pan circular magazine, somewhat similar (at least in principle) to the later Lewis Gun and some Russian WWII MGs.