England was only needed on Export pieces.
Frank — "ENGLAND" may not have been needed on personal imports into the USA up to some value? limit.
Barbara — Your vase is important to me for three reasons:-[list=1][*]It is the first vase known to me carrying the =S= mark,[*]It is the first piece known to me carrying both the Stuart and =S= marks, and,[*]It highlights our lack of knowledge of the British and American regulations concerning imports and the travelling public.[/list:o]Bernard C. 
What do you want to know about US import laws?
The marking of the country name is a Country of orgin issue not necessarily associated with duty. The purpose of the US tariff code being amended to include country of origin marking was so the American public could be informed as to the origin of the goods they were purchasing. The items are suppose to be marked in a legible and in a conspicuous place,e large enough and clear enough to be read easily by a person of normal vision. It need not be in the most conspicuous place, but it must be where it can be seen with a casual handling of the article.
The first US tariff code to require country of origin marking was the McKinley Tariff Act of 1890. This act required that the item be marked with the country of orgin, such as ENGLAND, JAPAN, etc. A subsequent tariff act modified these requirements and the items had to then be marked "Made In XXX" I think this changed around 1918 - I am looking to verify the specific date.
Edited to add:
Here is a summary of US tariff history
http://en.wikipedia.org/wiki/Tariff_in_American_historyYou can click on various links to get more info. I think the subsequent Act that modified the wording was the Payne Aldrich Act of 1909. But as with any US legislation which affects many stakeholders, there is a phase in date usually years in the future. You would have to go back to the specific text of that Act to find out the effective date. Even after the effective date you will have varying levels of compliance. We still have COOL issues 100 years later on imported goods.