The interpretation of the markings on pottery/ceramic items, and others, is quite often extremely complicated, but yet interesting. Here is some information on the mark "Foreign": "McKinley Tariff Act (1): Origin of the 'FOREIGN' marking:
On October 1st 1890 the Congress of the United States passed the so-called 'McKinley Tariff Act', a law that was introduced by the 25th President, William McKinley. This law not only imposed the highest tariffs that the United States had ever placed on imports, it also demanded that all items imported to the US, regardless of country of origin, had to be marked as 'FOREIGN'. This act was revised in two main steps: the first revision followed prompt, replacing the 'FOREIGN' with the true country of origin, based on the fact that Great Britain had already forced Germany to use 'Made in Germany' for their goods. The second step included the markings used by Japan and Czechoslovakia, as explained further below.
That aside, hold in mind that markings with 'FOREIGN' were indeed officially dropped, however their use represented a perfectly legal possibility of avoiding a true country mark when the target country had outlawed the corresponding country of origin. People may instantly conclude that this regarded German items created during World War 2, but that was only rarely the case.
Instead of vanishing from sight, the 'FOREIGN' mark was actually used on and off ever since its introduction, with various countries either using it or allowing imports showing such a mark. For example, West German potteries during the early Mid-Century-Modern era actually marked 'Foreign' for export to countries like Hungary or Bulgaria (as Western goods were not taken very well behind the Iron Curtain) while the U.S. accepted 'FOREIGN' marked imports from the U.S.S.R. during the Cold War.
So the mere presence of a 'FOREIGN' mark says absolutely nothing about the age or the intended target market of an item, in fact these items require intensive research as to place them correctly. Don't let yourself be fooled by sellers that claim a certain age (or country of origin) based simply on the presence of this mark."