cover 65c-$2.60 Graf Zeppelin (C13-C15), tied by 'Washington, D.C. Apr. 19, 1930' first day machine slogan cancels on separate matching air mail-bordered envelopes with typewritten address, 65c used domestically (not flown), others are cacheted Zeppelin flight covers, $2.60 cover has some green ink offset on the front (from the usual green Lakehurst receiving backstamp), it also has minor cover edge tears at both sides, otherwise fine-very fine, a very scarce set, Scott retail $4,850.00 (65c cover cataloged as a flown first day cover) photo ex