If the Colt Paterson was the high-end classy choice for a sidearm in the mid-1800s, the Allen & Thurber pepperbox would have been the simple working man's alternative. While Colt was working for military contracts, Allen & Thurber ignored that market in favor of producing an affordable civilian sidearm in large volume.
The basic idea of a pepperbox is like a revolver, but with the cylinder comprising a cluster of full-length barrels instead of just chambers lining up with a single barrel in turn. This made the pepperbox a simpler weapon to manufacture, as it did not have the precise alignment requirements of a traditional revolver. Allen & Thurber's examples were further simplified by having no sights and smooth bored, and being double action only.
These were not the tool of professional gunmen, but they were simple, cheap (a quarter the cost of a Colt), and effective enough at close range. Allen & Thurber sold a huge number of them (exact numbers are not known, as they were not serialized) during the 1830s, 40s, and 50s and made a very tidy profit in the process. The end of the pepperbox came as metallic cartridges were becoming common place, as there was no easy way to convert the from muzzleloading to cartridge use, and cheap revolvers would take their place as the stereotypical working man's handgun.