I'm not sure if this helps, but I read this today.
Due to the McKinley tariff act of 1890 products imported needed to be marked with their country of origin. In 1921 the law was changed so that the country of origin had to use their westernized name when marking imports. It also stipulated that the item had to marked "Made in"
So If an antique is not marked with a name it may be pre 1891. An item marked "Nippon" or "Japan", "Bavaria" or "Germany" might be made between 1891-1921. An item marked "Made in Japan" or "Made in Germany" is likely made after 1921.
I hope this information is correct.