The two series for Northants were:

Northamptonshire:

BD 1 to BD 9999

December 1903 to September 1924

RP 1 to RP 9999

October 1924 to March 1931

NV 1 to NV 9999

March 1931 to October 1937

BDA 1

Series started in July 1937, reversals started September1961

RPA1

Series started in August 1951, reversals started June 1960

NVA1

Series started in March 1956, no reversals

Northampton (borough) NH 1 to NH 9999

January 1904 to June 1930

VV 1 to VV 9999

June 1930 to January 1947

NHA1

Series started in July 1949, reversals started April 1960

VVA1

Series started in September 1959, no reversals