Cover franked with Chilean 1948 1p blue green (SG 379c) tied by fine boxed CORREOS DE BOLIVIA AMBULANTE No. 1 cancel in purple. Addressed to SANTIAGO with ANTOFAGASTA transit and SANTIAGO arrival cds's on reverse. Chilean stamps were generally allowed on this section of the railway as it formed part of the line from Bolivia to the port of Antofagasta and then on to the rest of Chile.