A theft-deterrent device (10) for application to an article to be protected includes first (20) and second (30) components adapted for locking engagement to secure the article therebetween, with a fragile vile (60) disposed within the first component containing a detrimental substance which would damage the article in the event the vial is fractured. A pin (15) protruding from the first component has a first end secured to the vial using a suitable attachment structure. The attachment structure provides an aperture which surrounds a portion of the “vial in a closely engaged arrangement, and also serves to rupture the vial and release the detrimental substance if unauthorized removal is attempted. The pin and the attachment structure can be integrally formed, or alternatively the attachment structure can be formed as a separate piece and attached to the pin.