Electronic apparatus and sensors for measuring layer thickness of coins, dental alloys, sterling silver, rhodium coatings, jewelry, precious metals and for testing coins, dental alloys, sterling silver, rhodium, coatings, jewelry, precious metals; X-ray fluorescence layer thickness measuring apparatus, not for medical purposes; electronic apparatus for non-destructive testing of coins, dental alloys, sterling silver, rhodium coatings, jewelry, precious metals; computer software for operating ...