official cachet on cover addressed to Miami, Florida, 20c Red violet (C11) tied by Cristobal machine cancel, prepared by Cristobal Postmaster Gerald D. Bliss with the signatures of Charles A. Lindbergh (pilot), Basil L. Rowe (co-pilot), and Igor I. Sikorsky (aircraft designer), very fine, one of just six covers prepared by Bliss with the signatures of Lindbergh, Rowe, and Sikorsky, a remarkable piece of aviation history