1918-1920 Offset Printing #525-536

1918-1920 Offset Printing #525-536
By 1918, the unavailability of high-quality German ink and key equipment overseas was impacting U.S. stamp printing. Impurities in the inks caused engraving plates to wear prematurely, then, the First Class letter rate was temporarily increased from 2¢ to 3¢. To quickly produce the needed 3¢ and 1¢ stamps, a switch was made from engraving to offset printing.