1917-19 5¢ Washington
U.S. #504 paid the Universal Postal Union international rate. It was printed in great quantities and current for six years. It is notable as the “correct” printing of a famous double-error stamp – U.S. #505.
Flat Plate, Perf. 11
The Bureau continued to use the 10 gauge perforation machines on flat plate stamp sheet 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.
5¢ Washington, issued to satisfy the UPU international rate
Issue Date: March 1917
Printed by: Bureau of Engraving and Printing
Printing Method: Flat plate, using plates of 400 with four panes with 100 stamps each