YEARS ago, my fathers company made these under license from a Finnish
company called Outokumpo Oy (sp?).  These were fiberglass bodies that went
around the entire conveyor.  The coils were wound on forms (I did a few of
these myself), and fed the electronics.  These were very sensitive units,
and eventually were designed to stand upright...you guessed it, airport
metal detectors.  This was way back in the 70's when skyjackings were
beginning to be common place.

No, he no longer builds these, but did put quite a few in place. And once
and a while, gets calls for replacement parts on them.