1917-19 11¢ Franklin
U.S. #511 found greater use than previous stamps of that denomination due to an increase in demand during World War I. The postal rate for domestic mail was increased to 3¢, which increased the rate for domestic and registered mail to 13¢. U.S. #511 was frequently used for that purpose when combined with a 2¢ stamp. It was also used in combination with other stamps to pay for heavier letters or foreign destination mail.
Flat Plate, Perf. 11
The Bureau of Engraving and Printing continued to use the 10 gauge perforation machines on flat plate stamp sheets even after 11 perf. stamps proved successful. In an effort to save money, they used the perf. 10 wheels until they wore out. Beginning in early 1917, stamps produced on flat plate presses were given 11 gauge perfs.
That marked the beginning of the flat plate perforated 11 Series of 1917-19 stamps. Perf. 12 had proven too flimsy, and perf. 10 was too difficult to separate without damaging the stamp, so perf. 11 became a satisfactory solution.
Issue Date: May 1917
Printed by: Bureau of Engraving and Printing
Printing Method: Flat plate
Color: Light green