A number of bistable magnetic devices are dispersed in a scanning region of a checking object. Each bistable magnetic device is formed of a nonmagnetic material which undergoes a drastic flux reversal attributable to the Large Barkhausen effect when subjected in succession to first and second external...http://www.google.com.au/patents/US5583333?utm_source=gb-gplus-sharePatent US5583333 - Checking objects including bistable magnetic devices, to be checked for authenticity
