Heavy duty registered cover franked with 1928 5c green & strip of three 10c slate (SG 221/222) plus 1928 15c green & 20c blue 'L.A.B.' AIR issue (SG 217/218) all tied by smudgy 'Airmail' roller cancel with COCHABAMBA CERTIFICADOS cds alongside & red on cream registration label. Sent airmail to USA with two $4 blue 'Volad por Aviones Junkers! Misoo Junkers Buenos Aires' aeroplane labels on reverse, both tied by USA arrival marks. Very Scarce.