The present invention relates to a wristwatch comprising a mechanical clock movement with a tuning fork resonator. The oscillator preferably comprises a material A with a low internal friction. In the oscillator of the invention, the unwanted symmetrical oscillations are avoided, for example, by the choice of the materials from which the tuning fork is manufactured. According to preferred embodiments, the rod and/or fastening of the oscillator comprises a material having greater internal friction than that of said material A, such that the quality factor Q.sub.2 of the symmetrical oscillations is reduced, in contrast to the quality factor Q.sub.1 of the anti symmetrical oscillation mode.

A balance spring for an oscillator of a timepiece, wherein it comprises a component part, in particular at least a coil or a portion of a coil, provided with heavily doped silicon having an ion density greater than or equal to 10.sup.18 at/cm.sup.3, in order to permit the thermo-compensation of the oscillator.

A piezoelectric balance spring (3) for a circuit (10) for self-regulating an oscillation frequency of an oscillating mechanical system (2, 3), or an energy recovery circuit or a motor circuit for actuating the movement or for the automatic maintenance thereof. The piezoelectric balance spring (3) includes at least one piezoelectric layer (7, 7, 17, 17, 27, 27) provided on a top face (20) or bottom face of a certain number of coils of the spring in a plane, and at least two pairs of electrodes (8a, 8b, 8c, 8d), whereby the electrodes of each pair are provided on two opposing faces of the same piezoelectric layer or respectively two piezoelectric layers so as to apply a reverse bias voltage on each pair of electrodes.

A device (100) for separating an assembly (10) of balance springs (12) which have been wound in and have undergone an expansion cycle, the device (100) including: a support (110) having notches (113) intended to receive the inner strands (13) of the wound in balance springs (12) making up the assembly (10), a vibrating table (120) movable along two different axes which extend in the same plane, defining a vibration plane (P1), the vibrating table (120) being configured to cause said support (110) to vibrate in a plane parallel to the vibration plane (P1). Also a method for manufacturing a balance spring.