Airmail cover franked with 1923 10c rose carmine and 1927 25c sepia & green AIR issue (SG 442 & 455) tied by MEXICO CITY cds dated 1 OCT 1928. Flown on the 'Mexico - Queretaro - Saltillo - Nuevo Laredo' first flight with boxed first flight cachet in black on front. Addressed to USA with transit & arrival marks on reverse. (Muller #12)