unused Block Larger Than four 8c-24c 1923 Air Post (C4-C6), plate no. blocks of six, 16c and 24c are L. plates, 8c is B. plate, all with full selvage, most stamps never hinged, some others have natural gum skips, 8c is fine-very fine, others have light perf. strengthening in selvage only, average centered, very good-fine set, Scott retail $4,875.00 photo ex