unused Block of Four 6c-24c 1918-23 Air Post (C1 two, C2, C3, C5, C6), blocks of four, one no. C1 and C3 with plate no., other no. C1 is L. arrow block of four, nos. C3 (stamps) and C5 never hinged, some h.r., some have faults, otherwise fine lot, Scott retail $1,395.00 est.