A system for bar code error detection in large volume mailings against a print run which prints the bar code on a mail piece. The etchant is prepared by combining precisely known quantities of the etchant components obtained from liquid sources of tetramethylammonium hydroxide and dissolved silicate. A pair of dies 6 each of which has a tapered portion 6b on an input side and a parallel portion 6b on an output side are used in at least part of the roughing process. The listener creates an instance of the client side plug-in and sends a channel accept to the terminal server. The payment device need not be changed for the rider’s fare.