The Zen Cart USPS shipping module for USPS RateV4 Intl RateV2 Mar 7, 2014 Version K3 can be used on the PRODUCTION server after USPS turns on the new Service Name changes for March 7, 2014, providing USPS has updated their Production Server. In the interim, the TEST SERVER or PRODUCTION SERVER can be used, for current USPS rate quotes.
If you are using USPS shipping module in your Zen Cart under tools modules, you need this upgrade to be able to serve the new, correct shipping prices, names and transit times.