Plunger lock

A lock comprising:

• a housing;
• shell means defining a keyway and longitudinally movable in said housing between a locked position and an unlocked position in response to actuation by a proper key in said keyway;
• and
• restraining means responsive to the key for selectively preventing and allowing the removal of said shell means from said housing means, said restraining means comprising a key responsive latch means movable between a shell latched position wherein removal of said shell from said housing is prevented and a shell removal position allowing removal of said shell from said housing, said latch means being concealed by said housing when moving into said removal position so as to be operable only by the key operably positioned in said keyway, said restraining means further comprising limit means for allowing longitudinal movement of said shell beyond said unlocked position only after rotational movement of said shell within said housing, and rotational restraining means for allowing said rotational movement only after movement of said latch means to said removal position in response to actuation of the key, said limit means comprising a mating slot and stop, and rotational restraining means comprising a restraining groove in said housing that is substantially parallel to said slot and slidably retains said latch means during longitudinal motion of said shell means.