Abnormal use indicator for door lock

In a door lock having,

• a cylinder housing for mounting within a door,
• a cylinder disposed for rotation within the housing,
• a row of radial channels in the housing,
• a matching row of radial channels in the cylinder, and
• spring loaded pins of selected lengths slidably disposed within said channels and adapted to be radially positioned by a profile section of a first selected key to permit rotation of the cylinder within the housing,
• the improvement comprising:
• at least one other channel radially disposed in the housing and in the cylinder at an angle apart from the first rows of channels,
• a further pin member slidably disposed in said other radial channel, the position of which is determined by the engaging surface of a second selected key,
• a spring loaded axial pin assembly disposed for axial movement within the housing, and
• restraining means urged radially outwardly by the further pin member for holding the axial pin assembly in an externally visible position,
• said restraining means being moved out of engagement with said axial pin assembly upon radial inward movement of the further pin member when engaged with a depressed profile section of the second selected key, allowing the release of the spring loaded axial pin assembly to the externally non-visible position in the door.