During 1992, in an international postal endeavor of unprecedented scope, the United States, Italy, Spain and Portugal (the four nations most closely associated with Columbus) each issued a set of six souvenir sheets on which all sixteen of the 1893 U.S. Columbian stamps were replicated. The sets of all four countries had been designed jointly and proved largely identical, differing only in details relating to language and national postal usage. The American issues reproduced the original stamps almost exactly but altered the date in the upper-right corner from 1892 to 1992.