Description: Air Mail Letter: BELGRADE - VIENNA, AUSTRIA 27.08.1924. Rare early letter twice re-addressed on arrival with attached labels. The letter is correctly franked on reverse with Din. 4.50 (Din. 3.00 for foreign letter and Din. 1.50 air surcharge). Red postmarks on air mail surcharge component. Three different WIEN arrival postmarks. Signs of ageing but overall fine and very rare.