Zeppelin Mail

Mixed franking of Hungarian and Austrian stamps on a Zeppelin cover carried on flight No.200 from Vienna to Friedrichshafen on 12 July 1931. Hungarian rate - 32f for a 20g letter plus and airmail fee of 16f to Austria. Austrian stamps total 3s 60 g making 40g letter rate to USA plus 3s 20g Zeppelin airmail fee. Probably unique.