United States, Airmails Collection. Accumulation of C20-22 20¢-50¢ Clipper Airmails, many plate blocks of 6 of all three values, as well as singles & blocks with plate numbers; well-balanced, mostly Very Fine and mostly never hinged, Scott catalogue value about $3,600, plate block of 6. Scott No. C20-C22  Estimate $750 - 1,000. $0