Roger

The Mexican oil industry was expropriated on 18 Mar 1938 and the state-owned Petróleos Mexicanos (PEMEX) formed on 7 June.

Her earlier history goes something like:
1910 completed by J T Eltringham & Co, South Shields (yd 274) as FLYING KESTREL for Alexandra Towing Co Ltd, Liverpool

1912 sold to S Pearson & Son Ltd, London as CERNICALO and transferred to the local company at Tampico, presumably Compania Naviera San Cristobal SA
[The Pearson company, previously involved in Mexico with civil construction projects was headed by Weetman Pearson. He was able to buy huge oil exploration concessions in 1901 and by 1908 had found huge reserves, formed the Mexican Eagle (Aguila) Company, and bought out local interests of Standard Oil. Pearson, by then Lord Cowdray, sold a majority stake in Mexican Eagle to Shell in 1919. This is the same Pearson company that is now has major media interests, including the newspaper "Financial Times"]
1938 transferred to Petróleos Mexicanos and renamed PEMEX I.

I wonder whether she appears in any of the other sources as PEMEX I?

David