Semi - Postal issues. 1919, black diagonal overprint ''Posta Ceskoslovenska. 1919'' over black ''FLUGPOST'' on Austrian 1.50k on 2k, 2.50k on 3k and 4k, complete set of three, full OG, NH, VF and scarce never hinged, expertized by J. Karasek and others, C.v. $1,000 as hinged, Pofis #52-54, CZK28,000=US$1,325 (Image)