Abstract: A method is disclosed for making an isochronous balance-wheel-and-spring assembly for a horological movement in which one spring out of a series of springs is paired with a balance wheel. The spring has characteristics that vary by comparison with other springs of the series, and the spring is designed to be mounted on the staff of the balance-wheel via a collet. One collet out of a set of collets of different sizes is selected on the basis of the spring's characteristics. The collets of different sizes have connection points for attachment of the spring that are located (after assembly) at different distances from the center of the balance staff, the choice of the collet of the most appropriate size facilitating the adjustment of the balance-wheel-and-spring assembly.

Abstract: The present invention relates to a tourbillon-type timepiece mechanism, comprising a cage (8-10), means (4) for pivoting this cage on a casing (1) of the timepiece, a kinematic link (3) between the axis of this cage and a motive barrel, a hairspring (13, 16) pivoted at the center of this cage and an escapement mechanism (19, 20) engaged with this hairspring (13, 16), the pinion (20a) of the escape wheel of this escapement mechanism (19, 20) being engaged with a toothing joined to said casing (1), which toothing is borne by a crown gear (21), connected to said casing (1) by an eccentric pivot pin (22a), and by means (22a, 22b) serving to immobilize said crown gear (21) relative to said eccentric pivot pin (22a).