1919, 2c. red surcharged "1er. Servicio Postal Aero 6-18-19" on flight cover from Barranquilla 18.JUN 19 to Puerto Colombia with arrival mark alongside, only 200 stamps were overprinted and 160 covers were carried aboard this flight operated by the American aviator William Knox Martin, signed and certificate Bloch (Friedl Expert Committee), Scott C1 (Image)