Horological mechanism for displaying at least the single time indication and timepiece comprising such a mechanism

A horological mechanism including a barrel drum mounted pivotally free around a barrel shaft, a barrel spring being housed inside the barrel drum, this barrel spring including a first external coil wherein it is attached to the barrel drum, and a last internal coil, the barrel spring being attached to the barrel shaft, the winding of the barrel spring being done by a winding rod which meshes with the barrel drum, a barrel ratchet being fixedly mounted on the barrel shaft, the horological mechanism also including a finishing geartrain which includes a first finishing wheel with which the barrel ratchet meshes and which transmits a driving force from the barrel drum to an escapement mobile the purpose of which is to maintain the oscillations of a regulating member which, by its oscillations, regulates the rate of the horological mechanism.