Registered airmail cover franked with single 1928 10p black & orange 'Presidente' AIR overprint issue with OVERPRINT IN BLUE (SG 197) tied by SANTIAGO ENCOMIENDAS cds dated 21 JUL 1928 with CORREO AEREO SANTIAGO cds alongside and boxed 'SANTIAGO' registration marking in black all on front. Addressed to ARGENTINA with arrival cds on reverse. Cover is a little grubby in places but an exceptionally rare stamp on cover.