1. A coin validation system for determining if a coin moving along a coin rail is a valid coin, and if so, its denomination comprising a rail along which coins move, coin sensor means located adjacent to the rail, said sensor means including at least one optical sensor for responding optically to movements of coins adjacent thereto, at least one magnetic sensor located in the vicinity of the optical sensor, said magnetic sensor including an inductive element, circuit means responsive to the optical sensor sensing the presence of a coin for energizing the magnetic sensor to produce a signal when the coin is moving adjacent thereto, the coin moving to a position to have mutual inductive cooperation with the inductive element whereby the inductive element produces an output signal having characteristics representative of the coin, signal preprocessing means operatively connected to the magnetic sensor including means for producing output responses representative of distinctive characteristics of the coin, feature extraction means for extracting from the output responses of the signal preprocessing means signal portions representative of predetermined distinctive features of the coin, means for producing a multi dimensional representation of the extracted features including a comparator circuit for comparing the multi dimensional representation with the center of an established cluster of selected coin denominations to determine the extent of the comparison therebetween such that when the comparison is of a certain nature the coin is determined to be acceptable and when the comparison is of a different nature the coin is not acceptable and artificial neural network classifier means having a first connection through first switch means to the feature extraction means and a second connection through other switch means to the comparator circuit, the artificial neural network classifier means having an output which identifies the denomination of coins that are determined by the comparator circuit to be acceptable.