A key having one end secured to a yoke mounted between in a casing to turn about a pivot axis between a position in which the key is retracted inside the casing and a position in which the key is extended, and a control pushbutton mounted in a housing of the yoke so as to be constrained to pivot therewith and so as to slide between a position for holding the yoke at least in the retracted position, and a position for releasing the yoke for pivoting, the control pushbutton having at least one stud received in a groove of the housing, the groove including an inlet segment that opens out via a first end in an outer face of the yoke and that opens out via a second end in a terminal segment, forming an angle therewith, the terminal segment extending along the pivot axis.