I remember reading about them back in the 80's I guess it was. Other than that magazine article, I've never "seen" one until now.
I remember in the story they told of a cop who lost his in a struggle, the perp pointed at him and tried to pull the trigger. Gun didn't work so he took off, with the gun. Later he took it to a gunsmith and told him something like this blank, blank old gun doesn't work. Smith removed the grips, saw the gizmo, knew what it was called the cops, who came by and recovered the gun and gave the bad guy a free ride downtown.
Pretty cool.