Kanatlarci SerbiaEthiopia Aérogramme / Air Letter stationery 30c ‘Airplane over Gondar Castle’ printed by Thomas de la Rue & Co. Ltd. on light blue paper with single flap at top and panels on both sides. Watermarked "Imperial / (castle) / K / Air Mail". Issued in October 1957.
[Basically, the 55-cent denomination was the rate for aerograms beyond Europe.]
Condition: Excellent, albeit with short vertical cut on flap; see scans.
If registered, please add 3 euros