A Civil Service Commission shall be established by Council and shall consist of three (3) electors of the Municipality, not holding other Municipal office or appointment, to be appointed by the Mayor, for terms of six (6) years each, except that of the three (3) appointed for a term beginning January 1, 1962, one (1) shall be appointed for a term of two (2) years, one (1) for a term of four (4) years, and one (1) for a term of six (6) years. A vacancy occurring during the term of any member of the Civil Service Commission shall be filled for the unexpired term in the manner authorized for an original appointment.