Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Switzerland - Pioneer Flights - 1930 (December 2), Ad Astra Aero Africa Flight registered cover delivered on leg Zurich - Cartagena - Alicante, franked by three stamps, blue flight cachet, undelivered and returned to Fribourg on December 11, appropriate markings on front and reverse, F/VF, Est. $100-$120, Scott #C9, C12