Airmail, 1935-37, China Clipper complete, set of three values in top margin plate blocks of 6, each on separate matching covers, 25¢ tied by "San Francisco, Calif., Nov 22, 1935" and 20¢ & 50¢ tied by "Washington, D.C., Feb 15, 1937" First Day of Issue barred duplex postmarks, 25¢ Special Delivery and other Registered usages to Indiana; some minor cover tone spots at right, still Very Fine, a very scarce First Day of Issue plate block set. Scott No. C20-C22  Estimate $300 - 400. $0 (Image)