A system includes a metal detector, a structure to hold the metal detector, and a processing unit which processes the measured signal from the metal detector. The measured signals of known objects are recorded with the metal detector. The signals are processed into sets of variables. When an unknown object is detected by the metal detector, the measured signal is processed into the same variables. The variables from the measured signal are compared against the variables in the database. If a match is found, the unknown object is determined.