Timepiece balance spring adjustment mechanism

A mechanism for adjusting an active length of a timepiece balance spring whose outer end is fixed to a balance spring stud secured to a bar, said mechanism including two pins for clamping or touching an outer coil of the balance spring during operation of said balance spring, wherein said two pins are in a single piece with said bar, and wherein at least said bar includes a position adjustable mechanism including a rigid carrier structure, using at least one elastic strip, of a position adjustable component carrying at least one of said pins and including an indexing means arranged to cooperate with a complementary indexing means comprised in an adjustment mechanism, said complementary indexing means being detachably mounted to the indexing means and being lockable in a cooperating position by a clamping mechanism elastically fixed to said structure, said clamping mechanism being in turn subjected to the action of a locking mechanism which allows said clamping mechanism to occupy either an uncoupled position wherein said adjustment mechanism is free, or a coupled position wherein said clamping mechanism hinders said adjustment mechanism, said locking mechanism being also elastically fixed to said structure.