Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Bulgaria - 1927-28, four Pioneer Flight Covers, two of Sofia - Varna and Rousse - Sofia of 1927; Sofia - Paris of 1928, each one appropriately franked, including air post adhesives, each one with arrival postmarks, mostly VF, Est. $250-$300 , Sc. #C1-4