Air Post stamps. 1941, First Flight Liberia - USA, black surcharges 50c on 4c, 5c, 10c and 30c (last one is NH), overprints on 50c (NH) and 1r (LH), full OG, VF, each one with Sanabria or J. Stolow guarantee hs, C.v. $470 as hinged (Image)