MAGNETS; MAGNETIC FIELD INDICATORS; ELECTROMAGNETIC DETECTION APPARATUS; PORTABLE MAGNETIC INSPECTION APPARATUS; ELECTRONIC POWDER DEVELOPER CABINET USED FOR TESTING AND ANALYZING METAL PARTS; ELECTRONIC PENETRANT LINE INSPECTION BOOTHS USED FOR ANALYZING AND INSPECTING METAL PARTS FOR FLAWS; AND ELECTRONIC CRACK CHECKING APPARATUS USED TO DETECT SURFACE CRACKS ON FERROUS AND NON-FERROUS METALS