Bidspirit auction | Worldwide Pioneer Flights - Bulgaria

Worldwide Pioneer Flights - Bulgaria - 1930 (May 13), flown cover from Sofia to Hamburg, franked by ten stamps, delivered by two connected Pioneer Flights Sofia - Nuremberg/Fürth and Nuremberg/Fürth - Hamburg, two appropriate air post markings on front, backstamped, punch at right, still F/VF and scarce, Est. $200-$300, Sc. #202, 211, C3