Many European manufacturers used to make folding shotguns and rifles designed to carry in a case while riding in a carriage or car. Typically late 1800s or very early 1900s. They had various names, but are typically small game guns for rabbits and such, usually chambered in a small gauge or small caliber. There should be a proof mark under the chamber area that will give some sort of idea of the country of origin, or perhaps a maker's name or inscription on the barrel or lock plate..