Upon receipt of the application and fee, the director shall register a serial number brand to the applicant. The serial number shall include a county number followed by an individual number. The county number shall be and remain the same as the number of the class of the county in the classification which was adopted by the Legislature in 1931. As to counties with classification numbers 1 to 9, inclusive, the county number shall be preceded by a dash (—). The county number shall be followed by a dash (—) and the individual number.