Registered cover franked with 1924 10c turquoise green 'Lapwing' issue and 1926 10c red 'Albatross' AIR issue (SG 456 & 496) tied by large boxed 'SERVICIO POSTAL AEREO MONTEVIDEO - BUENOS AIRES' cachet in red with registration label alongside tied by MONTEVIDEO cds dated 17. V. 1926. Flown on the Montevideo - Buenos Aires, Argentina first flight of the 19th May. Addressed to ARGENTINA with arrival cds dated 19 MAY 1926 on reverse. Uncommon flight. (Muller #18, rated 1500pts)