Royal Doulton
In 1815, John Doulton establishes a pottery factory in Lambeth, London, England. Royal Doulton initially produced utilitarian items such as pipes and jars. In 1877, John Doulton partners with Henry Doulton, his son, and the company becomes known as Doulton & Co.
M&A: Burslem Pottery Company(1901) - Royal Albert(1968) - Minton(1968 or 1972) Wedgwood(1993) - Fiskars
Today, Royal Doulton continues to operate as a subsidiary of Fiskars Corporation.
Royal Doulton Marks

c.1890

For export

c.1901 ~ 1930s

c.1922 ~ c.1927
If you examine the mark closely, you will notice that it has changed slightly.

1939

1972

2nd
Some marks have a year, as you see.
However, it does not always indicate the date of manufacture.
Recent

Cup

1990s ~