illustrated embodiment the locking discs 110 and the driving disc 120 are coaxially aligned along an axial centerline or axis c and together form at least a portion of the disc stack 104 while five locking discs 110 are shown in the illustrated embodiment it should be appreciated that the disc stack 104 may include more or fewer locking discs 110 each locking disc 110 is generally cylindrical in shape and may include a circumferential outer surface 111 a groove or indentation 112 formed in the circumferential outer surface 111 a keyway 114 positioned generally along the axial centerline c a radial protrusion 116 projecting radially beyond the circumferential outer surface 111 and a hooked shaped recess 118 extending between the circumferential outer surface 111 and the radial protrusion 116 in the illustrated embodiment the radial protrusion 116 has a first width w 1 at its radially distal extent i e farthest from the axial centerline c and a smaller second width w 2 at its radially proximal extent i e closest to the axial centerline c as should be appreciated the hooked shaped recess 118 provides the radial protrusion 116 with an undercut region the groove indentation 112 is sized and configured to receive the locking bar 102 fig2 and the keyway 114 is sized and configured to receive a corresponding mechanical key not shown in an aligned operational configuration position of the locking discs 110 the grooves indentations 112 are axially aligned with one another and or are axially aligned with the axial channel 132 in the plug housing 130 in a misaligned operational configuration position of the locking discs 110 the grooves indentations 112 are not.