unused Block of Four 6c-24c 1918 Air Post (C1-C3), L. and T. arrow blocks of four (24c consists of L. and B. arrow blocks) and center line block of four of each value, fresh, h.r., B. pairs never hinged, perfs. touch on some, two no. C1 stamps have P.O. staple holes which fall within the borders of the stamps, one no. C3 has small fault, otherwise very good-very fine 'set', Scott retail $4,230.00