Bosnia, Postage Due

,P 16, 21, Av. 221 (5),Cover (creased, affecting one stamp), franked with 75 hel. sent exspress - registered from Aussig (15.VII.19 - probable date error, 1918) to Sarajevo. On arrival 30 hel. Postage due was charged (20.VII.18). Rare use of postage due stamps.