From the official site, here:

http://www.hnwhite.com/Serial%20Numbers.htm

Brass King Serial Numbers
Date Serial Number
1893-1899 1-4,000
1900-1903 4,001-6,000
1904-1905 6,001-9,000
1905-1910 9,001-25,000
1910-1915 25,001-40,000
1915-1925 40,001-78,000
1925-1930 78,001-126,000
1930-1935 126,001-176,000
1935-1936 176,001-186,000
1936-1937 186,001-200,000
1937-1938 200,001-212,000
1938-1939 212,001-225,000
1939-1940 225,001-239,000
1940-1941 239,001-254,000
1941-1942 254,001-264,000
1942-1945 264,001-267,500
1945-1946 267,501-277,000
1946-1947 277,001-287,000
1947-1948 287,001-296,500
1948-1949 296,501-301,500
1949-1950 301,501-308,000
1950-1951 308,001-316,500
1951-1952 316,501-322,000
1952-1953 322,001-330,000
1953-1954 330,001-337,000
1954-1955 337,001-340,000
1955-1960 340,001-370,000
1960-1965 370,000-406,500
1965-1970 406,501-457,600