The 1-cent Balboa stamp features a portrait of Vasco Nunez de Balboa, the Spanish conquistador who is recognized as the first European to see the Pacific Ocean. Apparently issued in January 1907, its earliest recorded usage was January 14, 1907, making it the last stamp issued of the set. It paid primarily the postage on domestic post cards.
This stamp was printed with a number of obvious errors, including missing perforations vertically, horizontally, double overprints, and missing letters. One of the most spectacular errors and a favorite for both collectors and non-collectors is the issue with an inverted center and the overprint reading up. About twenty-two unused and thirteen used copies are known to exist.