Circa 1937 undated cover with manuscript 'Par Avion' at top franked with pair 1935 1½ Bs. orange yellow 'Map' issue, 1937 12 Bs. On 10c 10c black & orange red AIRMAIL issue with 'Correo Aereo D.S.' surcharge and 1938 60c deep blue (SG 304, 326 & 341) all tied by undated LA PAZ SERVICIO AEREO POSTAL cancels in purple. Addressed to SWITZERLAND. The airmail surcharges are uncommon used on cover.