cover 1c-10c Kans.-Nebr. overprints (658-679), complete sets, tied by 'Washington D.C. May 1, 1929' first day machine slogan pmks. on separate covers, 1c and 1½c values in horizontal pairs, 9c Nebr. run through machine canceler upside down necessitating additional duplex first day cancel, very fresh and neat matched set of first day covers, fine-very fine, Scott retail $1,377.50