In this 1938 poster, sacks and crates of products from "fascist Spain" have been stamped with the word "boycott." The swastika serves as a reminder of the ties between fascist Spain and Nazi Germany. The products lie to the side of the railroad tracks as the train appears to be passing them by. The image matches the message of the poster admonishing French railroad workers not to carry products from fascist Spain.
The text of the poster is written in French, which places this poster among many others produced by Republican Spain that sought to internationalize the conflict of the Civil War. In particular, the Republican government tried repeatedly to obtain support from the governments of Western liberal democracies, such as Britain and France. In fact, a Non-Intervention Committee was formed at the urging of both Italy and Britain in September 1936. With the ravages of World War I still in recent memory, the goal was to confine the fighting to Spain and to block the sale of weapons to either side of the conflict. Ultimately, the committee failed as Germany and Italy provided much aid and military support to Franco and the Nationalists while Republican Spain received help from the USSR since Britain and France were reluctant to get involved.
In this context, this poster appears as an attempt to get France involved in the conflict without necessarily breaking the precedents of the Non-Intervention Committee. Other examples of such attempts by the various groups of Republican Spain to internationalize the Spanish Civil war include posters 65, 80, and 89.