$1 1935-A Silver Cert, Fr. 1609 "R Experimental" Red R Fine

During the military mobilization of WWII, the U.S. government was concerned about the availability of currency paper. So new paper designed to be more durable was tested in hopes of extending the life of bank notes. On a single day in 1944, the Bureau of Engraving and Printing issued Series 1935-A $1 Silver Certificates on the special test paper – overprinted with a prominent red "S." An equal number of Silver Certificates on regular paper were issued on the same day with a red "R" overprint. The BEP planned to compare the condition of the notes as they were redeemed. The test later proved inconclusive, but the notes remain wildly sought after.