(a) In municipalities with a population of 500,000 or more, the municipal clerk may appoint the number of deputy clerks necessary to discharge the functions and duties of the office of municipal clerk.
     (b) In municipalities of less than 500,000, the municipal clerk, when authorized by the corporate authorities, may appoint the number of deputy clerks necessary to discharge the functions and duties of the office of municipal clerk, who need not be a resident of the municipality. The corporate authorities of the municipality may limit the number of deputy clerks that the municipal clerk may appoint.