BANKNOTE VALIDATOR

A banknote validator can recognise ink stains having predetermined characteristics and is operable to perform measurements on a received banknote in order to classify the banknote into at least the following categories: (a) genuine non-stained bills of said denomination; (b) bills which been stained; and (c) other bills, including non-genuine banknotes. Preferably, stained banknotes are sent to at least one dedicated store. The validator can classify banknotes into many denominations, but can only authenticate banknotes belonging to a sub-set of those denominations.