Poster stamps are just what their name suggests: posters in the form of postage stamps. Small, colorful, appealing to all, the first poster stamps to appear are generally credited to printers from Germany who called them reklame marken. In the United States, businesses first benefited from poster stamps, using them for advertising purposes. They were distributed by the thousands, cost little, and reached a wide audience easily. Subsequently, they were used to promote expositions, sporting events, charities, and other activities of public interest. By 1915, Americans were avid collectors. During World War II, civil organizations used poster stamps for patriotic purposes. Prominent artists lent their talents to designing poster stamps, including Edward Penfield, Maxfield Parrish and and Rockwell Kent.
The Emeralite Poster Stamps were printed by Wentz & Co., Germany.
Since the lamps pictured in the stamps are very early versions of model 4378 lamps, the stamps were likely made in 1909, or shortly thereafter.