1936 German Air Mail (""Deutsche Luftpost"") stamps C57 (50pf) and C58 (75pf) issued for franking mails to be carried on the airship ""Hindenburg"" (D-LZ129) from Germany to North America (""Mit LZ129 nach Nordamerika"") postmarked (CDS) at Friedchshafen on March 26, 1936, for a cover carried on Rheinland Referendum Flight (""Die Deutschlandfahrt""), March 26-29, 1936. (Source: "The Cooper Collection of Zeppelin Postal History")