Sought-after pairing of two six-stamp plate blocks of $2 Federal Duck Stamps of 1955 and 1956: the 1955 example featuring an illustration of blue geese by Stanley Stearns (RW22, VF centered and mint, never hinged); and the 1956 example featuring American mergansers by Edward J. Bierly (RW23, VF centered and mint, never hinged). Issued by the U.S. Department of the Interior as a "Migratory Bird Hunting Stamp," each stamp carries a warning on the reverse: "It is unlawful to hunt waterfowl unless you sign your name in ink on the face of this stamp."