cover 3c Green (207), block of six (3x2), used with single 2c Vermilion (183) on reverse of 1883 registered cover to Italy, with stamp dealer corner card, tied by N.Y. double oval registry pmks., indistinct violet registry c.d.s., additional blue pencil registry markings, Modena backstamp, blocks are legitimately scarce used on cover, an unusual foreign registry usage, very fine, with 1990 P.F. certificate