Cover franked with 3 x 1950 30c orange (SG 882) tied by three fine strikes of undated OFICINA DE CORREOS LA CONCEPCION. CAMPO PETROLERO EDO ZULIA 'Arms' cancel in turquoise blue. Sent airmail to HOLLAND with oval MARACAIBO transit mark on reverse. This was the P.O. for the workers at the Petroleum Plant. Uncommon.