Just finished some research on the Actionless. It definitely is not fitted on the circle, while it was made with interchangeable barrels in smooth and rifled calibers, changeable by the owner with no tools. Note that the barrels came apart via a snap near the loop and could be assembled again with no tools in any mix the owner wanted- smoothXsmooth, smoothXrifled, rifledXrifled. The ones the search uncovered were proofed in Paris and their proof pressures were higher than most.

The puzzling thing is how this gun survived in the absence of a solid action bar, reinforcements and circle fitting etc. Discoveries like this one show that double gun design is largely uncharted territory.