Banknote Serial Number Verifier - Version 1.0 We offer a wide range of money counters, cash counters, money detectors, and other cash handling equipment. This USD banknote serial number verifier is designed to check whether the serial number of a given banknote is valid. A valid serial number is not sufficient to confirm banknote's origin. However, an invalid banknote serial number is a sure sign that a banknote is counterfeit.