A first lower case member open at the top thereof supports a magnet therein for establishing {TAIL ~ a magnetic field} oriented parallel to {HEAD ~ a central axis} of the lower case 
A first lower case member open at the top thereof supports a magnet therein for establishing { TAIL ~ a magnetic field } oriented parallel to { HEAD ~ a central axis } of the lower case
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH