Nut-locking device and associated assembly unit

Assembly for a locking device, extending along a main axis (X) and comprising:

• a nut comprising a first and a second coaxial and opposite-direction tappings;
• and
• a ring;
• an inner surface of said ring comprising a third tapping;
• the first and third tappings being capable of cooperating with a same first thread;
• an outer surface of said ring comprises a second thread capable of cooperating with the second tapping of the nut;
• characterized in that:
• a portion of the ring, in radial external projection with respect to the second thread, comprises at least one through hole along the main axis (X);
• and
• a surface of the nut, perpendicular to the main axis, comprises at least one visual marking,
• said at least one visual marking being configured to be facing the at least one through-hole when the nut and the ring are in an installation position, and away from said at least one through-hole when the nut and the ring are out of said installation position.