I'm not sure the one in the pic is a pepperbox since it has one barrel.
I too do not see a classic Pepperbox, rather an early concept of a revolver. ..
NOW, If you look at the rear boss or breach end of the barrel, you will notice a cut-out of entrance ramp that would allow you to load both powder and ball, much like the standard C&B revolvers. What is missing here, is the loading lever or rod. You will also notice that the cylinder is short. What I suspect they did, was load a light powder charge and just pushed the ball in, until it was flush or cleared the barrel. This could be done with just about and flat surface. Not much room for a short start. ....
I also find the cap loading access, to favor a right hand shooter. ....
Be Safe !!!