Abstract: An antitheft security system is disclosed for automotive, marine, and other valuable personal articles such as objects of art and valuable collectible objects. A dealer/installer is provided with equipment comprising a main unit having a memory, a keyboard for data entry, and a visual screen for monitoring the data entry procedure and also for displaying to the dealer the precise locations on the article where it is to be marked. The unit randomly selects different marking locations on the article by calling up form its memory a programmed universe of several hundred possible marking sites for each particular type of item. An image of the item is displayed on the visual screen, which indicates the exact location where each marking is to be made. The security codes are applied by a portable hand-held marking head containing an electrostatic, noncontact ink jet spraying nozzle which invisibly microprints a unique, classified security code in a dot matrix format of alphanumeric characters onto the surface.