> very few objects with a comparable quantity of metal in them as a gun would routinely be carried into a casino.

I'm not sure this is true at all. A backpack with a frame has more metal than my pocket pistol, as does my MacBook Pro.

Is this system capable of discriminating between various types of metal? I know many hobby metal detectors these days can give you an idea of the conductivity of a buried target, although that can vary wildly based on depth and orientation, and is limited to about a foot or so in soil.