Window envelope franked with 1917 block of four 1c green 'National' issue and 1923 30c dull blue SCADTA issue (SG 358 & 41) tied by MEDELLIN SCADTA cds's dated 21. V. 1929. The cover would have been addressed to USA with fine strike of unframed 'PANAMA - COLOMBIA - ECUADOR Use the SCADTA Airway System, Saves about 10 Days, Information and Stamps through Illinois Merchants Trust Co. 231 South La Salle Street CHICAGO, ILL // Enrique Naranjo 10 High Street BOSTON, MASS.' American consular agents cachet in blue green on reverse with BARRANQUILLA transit cds alongside. A very scarce cachet.