Cover from the 'Tropical Oil Company' franked with 1923 8c blue national issue and 1923 30c blue SCADTA issue (SG 397 & 41) tied by BARRANCA-BERMEIJA SCADTA cds's. Addressed to CRISTOBAL, CANAL ZONE with fine strike of boxed 'Aproveche Ud el Servicio Postal Aereo de Colombia, Informacion y Estampillas donde PANAMA AGENCIES Co. LTD, Panama' Panamanian consular agents cachet in blue on reverse with blue BARRANQUILLA transit cds on front. Very scarce.