U/W ULTRASONIC EDDY CURRENT INSPECTION INSTRUMENT; REF PART W/BUILT-IN DEFECT & UPPER SKIN REPRESENTATIVE OF FIBERGLASS SKIN TO BE CHECKED W/ AL BACK-UP REPRESENTATIVE OF AL ACFT PART IS UTILIZED TO SET UP INSPECTION EQUIP.; USED TO TEST FIBERGLASS-TO-AL BOND LINE OF VERTICAL STABILIZER VHF ANTENNA ASSY