sentences:  Perhaps their most popular stamps were the Columbian Issue, one cent to $5 issues commemorating the voyages of Christopher Columbus and the 1892–93 Columbian Exposition (for which they had also printed the admission tickets) in Chicago.On July 1, 1894 American delivered its entire stamp-producing operation to the U.S. Bureau of Engraving and Printing in Washington, D.C., where U.S. stamps were still printed up into the 1990s.In 1933, the company printed the second series of Bank Melli Iran banknotes.