A quantity of Series 1935A $1 Silver Certificates was used for a currency paper experiment. The notes were overprinted in red, to the right of the Treasury seal, with a large "R" for regular paper or a large "S" for special paper. This Series 1935A-R $1 Silver Certificate bears the "R" overprint and has Julian-Morgenthau signatures. Once redeemable for silver coin or bullion, small-size Silver Certificates are among the most sought-after U.S. currency notes.