Rotor for a rotor-type locking device that is at least opened by rotating along a rotation axis the rotor within a housing of a stator by means of an operating key provided with operating means on one of its faces to operate movement of tumblers, said rotor comprising a body with a front end and a back end, said body featuring: - a central chamber with at least one front aperture located at the front end and adapted for the introduction of at least one portion of the key into the chamber, said central chamber having at least a first inner face adapted to be in front of a face or edge of the operating key, and a second inner face opposite to the first inner face, said first and second inner faces of the central chamber being preferably the faces of the central chamber having the smallest width; - a series of slots which communicate with the central chamber, whereby a first slot is adjacent to the front aperture, and whereby adjacent slots are connected the one to the other by one or more bridges; - at least four locking tumblers (12, 13) which respectively slide in a slot under the action of one or more return means, each tumbler (12, 13) presenting a control nib (12A, 13A) designed to cooperate with the key introduced into the central chamber, so as to bring each tumbler into the unlocking position against the action of one or more return means, more particularly one or more return springs; and - at least one weakening zone adapted for enabling a rupture or fracture in the rotor when a rotation of the rotor in the housing of the stator is commanded by means of a tool different from the operating key, whereby, when a rotation of the rotor is commanded by means of a tool not being the operating key, at least one weakening zone (WZ1,WZ2) is located between the front end and the first slot, is adapted for generating a rupture or fracture in the rotor at least from the front end at least up to the first slot substantially in a plane comprising the rotation axis or substantially in a plane parallel to the rotation axis. - a central chamber with at least one front aperture located at the front end and adapted for the introduction of at least one portion of the key into the chamber, said central chamber having at least a first inner face adapted to be in front of a face or edge of the operating key, and a second inner face opposite to the first inner face, said first and second inner faces of the central chamber being preferably the faces of the central chamber having the smallest width; - a series of slots which communicate with the central chamber, whereby a first slot is adjacent to the front aperture, and whereby adjacent slots are connected the one to the other by one or more bridges; - at least four locking tumblers (12, 13) which respectively slide in a slot under the action of one or more return means, each tumbler (12, 13) presenting a control nib (12A, 13A) designed to cooperate with the key introduced into the central chamber, so as to bring each tumbler into the unlocking position against the action of one or more return means, more particularly one or more return springs; and - at least one weakening zone adapted for enabling a rupture or fracture in the rotor when a rotation of the rotor in the housing of the stator is commanded by means of a tool different from the operating key,