Penguin Sheet of 20 Additional Ounce Stamps Scott 4989 by USPS This beautiful stamp from the U.S. Postal Service pays tribute to the majestic emperor penguin (Aptenodytes forsteri). Largest of the penguin species, the emperor stands over three feet tall and can weigh more than 80 pounds. The stamp art is a stylized drawing of a pair of emperor penguins on a cool green background. Illustrator Nancy Stahl hand-sketched and then digitally composed the art based on photos she took of emperor penguins at the Central Park Zoo in New York City. Art director Carl Herrman designed the stamp. Penguins is being issued in self-adhesive sheets of 20 and coils of 100 stamps. The words ADDITIONAL OUNCE on this stamp indicate its usage value. Like a Forever stamp,