Legitimate stamps have certain authenticity features such as phosphor tagging that Post NL security systems automatically check as letters and packages go through the sort process. Post NL said the sheets of stamps have mostly been encountered on registered letters and parcels, which could have cost the company millions of euros in damages if they had not been intercepted.
Dutch authorities have been brought in to investigate the case.
Production or use of counterfeit stamps is punishable by up to six years in jail.
