Early in 1917, the Post Office was caught off guard by a sudden huge demand for high-value stamps. At that time, Americans were sending many shipments of machine parts to Russia by Parcel Post. Also, valuable shipments of Liberty Bonds required large amounts of postage. To meet demand, the 1918 $5 Franklin stamp was issued. The bi-color stamp features a deep green frame and black central design on unwatermarked paper. The perforation gauge had been changed to 11 the previous year, which defines this sixth major set in the Washington-Franklins. A $2 Franklin stamp (U.S. #523) was also issued to meet the sudden demand for high-value stamps. The denominations were nearly identical in design, with different colors to help postal clerks tell them apart. Because of its high face value and postal use, U.S. #524 has always been desirable. In “United States Postage Stamps 1902-1935,” philatelic author and legendary stamp expert Max Johl advised, “Only a limited number were issued and collectors would do well to buy their copies... as soon as possible, as this stamp will soon be among those ‘hard to get.’